Perhaps this direct comparison of the specifications and features of these tools will be helpful to you. Even if you don't agree with my conclusions or importance of certain tool features, this side-by-side comparisons should at least provide you with food for thought.
If you're looking for an impact driver performance comparison, this isn't it. (But, I own and use a Makita BTD144 & my comments on that tool ARE based on actual use.) The purpose of this comparison is to save you the work of collecting, collating, and documenting the specifications of each tool, so you can do your own [specification & feature] comparison. Manufacturer's specifications were taken at face value, since, for example, I have no way to verify torque or RPM data. To the extent that part of your buying decision is based on manufacturer's specifications & features, this should be of some help. To the extent that your decision is based on actual tool performance, you'll need to read other tool reviews.
I initially did this because of disappointment in the impact driver review in Fine Woodworking's 2010 Tool Guide. They didn't test this Makita driver, or the DeWalt, Milwaukee, Bosch, or Hilti models listed below.
My goal was to select the "best overall" professional caliber cordless impact driver with high capacity (e.g., 3.0 amp hour) lithium ion batteries. That ruled out brands such as Ryobi, Black & Decker, Sears, and Rockwell. Also, I had no interest in hybrid impact driver/drills such as the Makita BTP140 or Bosch 26618-01 since I already own other cordless drill/drivers and hammer/drivers.
The Ridgid R8823 flunked early-on because there were numerous negative reviews; from Fine Woodworking and others. Our local Home Depot sells the tool only (no batteries or charger) for fifty bucks, which could imply they are phasing this model out.
The initial culling resulted in the latest & greatest models from seven manufacturers. Keep in mind that when newer models are introduced, much of this information could change. (I use tools from all of these brands and have no favorites. No one company makes the best tool of every type.) Here are the seven models:
1. Hilti.. 3 lamps 120 degrees apart, around the bit holder, runs off tool battery
2. Makita: stays on 10 seconds after tool is off; has switch to use it as a mini-flashlight
3. Bosch, Milwaukee, Panasonic, DeWalt: yes, runs off tool battery
4. Hitachi: yes, in the belt hook, requires 2 AAAA batteries & it must be aimed.
Tool weight with battery:
1. Panasonic....: 3.1 lbs.
2. Milwaukee....: 3.2 lbs.
3. Makita.........: 3.3 lbs
4. Hitachi.........: 3.5 lbs.
....Hilti.............: 3.5 lbs.
5...DeWalt........: 3.7 lbs.
6...Bosch..........: 3.8 lbs.
Battery charge time:
1. DeWalt, Makita, Hitachi, Bosch: 30 minutes
2. Panasonic....: 50 minutes
3. Milwaukee....: 60 minutes
4. Hilti.............: unknown (Hilti specs don't say and they wouldn't answer this question)
Internet/Amazon cost (as of this writing, highly subject to change & price shopping):
1. Hitachi........: 240
2. Milwaukee....: 297
3. Panasonic....: 299
4. Bosch..........: 317
5. DeWalt........: 329
6. Makita.........: 330
7. Hilti.............: 359
Conclusion:
All seven models deliver [approximately] triple the 450 in./lb. torque of a typical 18v cordless drill/driver, with no counter-torque to your wrist. All models are ambidextrous; i.e., they work the same in either hand. All models feature a 1/4" hex socket with a snap-chuck to securely hold drill or driver bits. Impact drivers can be quite noisy when "impacting" and all are reversible with variable speed triggers. The four multi-speed models use electronics versus a gear box, which is a good thing. (I.e., drills that change their speed range via a sliding switch connected to the gearbox can strip gears if said switch is moved while the tool is running.)
Depending on which factors are most important to you, your [specification & feature] rating won't necessarily agree with this conclusion. That is, having multiple speed/torque choices was paramount to me; 2 speeds are better than 1, and 3 speeds are better than 2. Having a short tool so it would fit in tight quarters was also important, as was being light-weight. Maximum torque wasn't particularly important to me, since these models are pretty close in that department, and all are quite powerful.
Also, recognize that no model is the best in every area, be it warranty, charge time, tool length, or whatever. Price had little sway in these rankings, other than designating the Hitachi "best value" because of its lower cost.
My ratings from 7 to 1, with number 1 being best overall:
7. Bosch: Having only a single speed/power choice is a serious deficiency, in my opinion. One speed is probably fine for carpentry, but one speed/power setting severely limits tool flexibility. E.g., it's too easy to snap or "over" drive a smaller screw when 1,400 in. lbs. of torque is your only choice and the sole method of controlling all that power is feathering the trigger. To be competitive, Bosch's next generation impact driver needs multiple speeds. Bosch's three-year tool warranty (1st year free replacement, 2 more years free repair), and their 2 year battery warranty is fourth best. This is the heaviest of the seven models. If these batteries fit other Bosch tools you own, that would be a good reason to buy this model.
6. Milwaukee: Their lithium batteries have a level-of-charge indicator; press a button and 1 to 4 led's show power remaining. This is very useful job-site feature, since otherwise, there's no way to tell how close a battery is to needing a recharge, before climbing the ladder, etc. Has one speed only; a serious deficiency. Milwaukee doesn't divulge battery amp hours. Batteries have the longest charge time (60 minutes, versus 30 minutes for most of the others). However, Milwaukee has the best tool & battery warranty of these manufacturers. My several Milwaukee power tools are all first-rate.
5. DeWalt: This single speed tool gets excellent customer reviews, but so does the Hitachi, which costs less and has two speed/power selections (0-2,000 RPM & 0-2,600 RPM). No tool case is included. Impressive "NANO" battery technology with a claimed 2,000 recharges. (An important tool selection factor if you will be recharging batteries daily.) Second best warranty: 3-years tool/charger/batteries, 1-year tool service contract; 90-day money-back. DeWalt doesn't divulge battery amp hours. Second heaviest of the seven models at 3.6 lbs. Would be much more versatile if it had 3 speeds, like the Makita & Panasonic.
4. Hilti: Fifth best warranty (see their web site for details); 2 speed/power choices; case is included; most expensive and one of the longest models @ 6 3/8". The only suppliers I could find were Home Depot and Hilti's web site. Only model with a wrist strap to reduce chances of dropping the tool; e.g., you're on a ladder. One of two models (along with Milwaukee) with a battery level-of-charge indicator; very useful feature before climbing that ladder. Hilti's specs don't say how long it takes for a battery charge, and Hilti never responded when I asked that question of their corporate sales unit. The battery has less amp hours (2.6 Ah) than the other models, but the tool has excellent ergonomics and is very well balanced. The Hilti has similar specs to the Hitachi, and I would have ranked them the same, but the Hitachi has a better tool warranty and costs much less.
3. Hitachi: Best value. Has an excellent tool & battery warranty and two good speed/power choices. The belt hook is easier than most to latch onto your belt without looking. It's been on the market for over two years, so a newer model may be coming soon; customer reviews are consistently positive on this model. If the tool is used after the battery becomes noticeably weaker, the battery may become damaged or its life may be shortened (according to the Hitachi WH18DL user manual). No tool case is included.
2. Panasonic: Based on other reviews I found, this driver has one serious flaw in that the handle breaks too easily if the tool is dropped. To exacerbate that issue, there doesn't seem to be any web site, including Panasonic's, that sells replacement handle parts for this tool; so an expensive service center would be your only choice. Perhaps those handle breaks were flukes, but those anecdotal reports made me nervous, even though it's clearly 2nd overall best otherwise, and I have other [terrific] Panasonic cordless tools. (I have been known to drop a tool from a ladder - last time it was my Milwaukee V28 hammer drill -- 8' onto concrete and nothing broke.) Panasonic has the worst warranty of the seven manufacturers; is the longest model at 6 ", and has a long (50 minutes) recharge. On the plus side, it has three excellent speed/power choices making it extremely versatile, a belt hook that's easy to latch onto your belt without looking, and comes with a case; Fine Woodworking's 2010 Tool Guide rated this model Editor's Choice Best Overall, of the models tested. However, FW doesn't do drop tests, and the Makita (model BTD144) wasn't tested by them, perhaps because it had just come to market.
1. Makita. Best overall. The variable three-speed/power selection switch offers soft, medium and hard settings* for a wide range of fastening tasks. Having a brush-less motor is one reason this is the shortest impact driver (to fit in small spaces), since motors with brushes are longer. Brush-less motors also reduce [mechanical] complexity and maintenance, since..., there are no brushes. Makita makes 34 other cordless tools that use the same batteries as this one. The easy-to-grab bit-holder protrudes 5/8" from the tool to simplify bit changes. Bits slide in and out of the bit holder by just over 1/16". The black material surrounding the tool handle is rubber, for tool protection and comfort. My XXL glove-size hand fits the handle just fine, and nothing pinches the fingers. This is the latest generation Makita impact driver, introduced summer 2009 and has their most advanced battery technology, an electric brake, and a phosphorescent bumper ring for finding the tool in dark spaces. There's also a battery warning light and bright built-in LED; both flash when it's time to recharge the battery. It has the right speed/torque setting for anything from heavy construction, to finish carpentry, to cabinet-making. Two "improvements" would be for Makita to lengthen the battery warranty to two or more years, and to include a battery level-of-charge indicator as found on the Milwaukee and Hilti models.
I was tempted to buy the less costly Hitachi, but selected the better, and more expensive, Makita BTD144 - and have no regrets. This is a terrific tool, which I now use instead of my two Panasonic 15.6 drill/drivers for driving screws, and even for some drilling.
* soft: 220 inch pounds of torque -- medium:490 in. lb. - hard: 1420 in. lb.
