Cordless drill, Amps vs Volts, fabricators?

As others have mentioned, it's the product of voltage and current that gives power, which is closer to what you'd like to compare to determine the force with which a drill can turn the bit. Also, Amp-hrs are more a measure of battery capacity -- how long the battery can deliver current -- so even multiplying voltage by an Amp-hour parameter isn't really what you want. (Nod to Astrobuf for mentioning this first.)

Closer would be the Max Torque parameter (in-lbs) which measures turning force combined with Max Speed (RPM). Here is a graph of Max Torque vs Max speed for popular drill drivers:

http://www.howtodecide.com/cordless-drill/#~tf.max...

Milwaukee 2610-24 and Bosch 37618-01 lead there with 650 in-lbs and 1800 RPM. (DeWalt is missing, however, because they chose not to publish Max Torque, claiming that it's a not a fair way to specify delivered turning power.) You can explore other combinations and trade-offs with other factors graphed against each other too, including voltage, current, battery type, weight, etc. (Don't overlook weight in your consideration as it's usually a heaver drill that can deliver the most power, but they can get to be a pain to hold for the majority of jobs.)

Battery type: I prefer Li-Ion in general because I like to put my spare on the charger without worrying how much charge it might have. Carefree charging is more important to me than having a smooth drop-off as the battery looses power. NiCd's have that memory effect where you're only supposed to charge it after it's fully discharged. Li-Ion batteries also are lighter, which offsets some of the added weight of a 18v.

Volts Vs Amps

You are misreading the spec's. The 3.5 Amp-hour rating you cite is the battery capacity. That means, it can supply 3.5 amps for 1 hour or 1 amp for 3.5 hours or some other equal product, i.e 14 amps for 15 minutes.

What's most important in a cordless tool is the motor power. This is measured in Watts and is the product of Amps x Volts. So an 18 volt battery running at 10 amps will produce 180 Watts of power in the motor. Your 3.5 amp-hour battery could do this for about 20 minutes.

In general, higher voltage batteries and motors are more efficient

Lithium Ion batteries pack much more power into a given volume than do Ni-MH and NiCd. While they do have the run hard and stop mode, they will run much longer than NiCd and longer than NiMH. They also charge faster and are easier to operate due to their light weight. Li-Ion batteries have lower internal resistance which means they can supply more peak current and thus produce more power than can NiCD or NiMH.

As much as you like Panny drills, I think you'd be better off with a Makita or a DeWalt. Better value and better performance as measured by most independent tool testers.

Astrobuf

Power is a function of volts times amps. A tool rated at 18 volts and 3 amps would have the same theoretical power as one rated 15.6 volts and 3.5 amps.

I used a Panasonic drill until it gave up (after I dropped it in a swimming pool) last year.

I picked up a Ryobi because it was on sale but have been amazed at how much longer the battery seems to last. Yes, when it quits, it does so abruptly, but it came with two batteries, one of which I leave on the charger so I can always keep going. And yes, I like the lighter tool and think it makes me more productive because my wrist doesn't get tired as quickly.

Of course, I don't use it every day or even every week, but when I do use it to build a deck or dock or something, it gets a heavy workout.

I use Dewalt Drill, with a cord--that way i don't have to worry about charging it. Most of all the not corded ones loose power, I need to get the job done, not play with it waiting for drill to recharge. Yes im a female, actually have 2, one is going to the hall of fame for drills it lasted 12 years of me.

The newer batteries last a lot longer. Many drills come with two batteries so you can keep one charged.