[Bob Steele]

Our team uses the Dewalt 20 series.
We have had no issue with them.... we also use the Dewalt 12 volt lithium series and in 2015 we had to assemble on the field and the Dewalt 12 volt screwdrivers worked really well to speed that up.

We used to use the old Nicad Dewalt 18 volt tools and before that the 14.4 volt Dewalts.
Whatever you do, you need to choose something and then stick with it. Having a number of different systems around only makes it confusing.

Something else that Dewalt has is an adapter to use their 20 volt batteries on the older 18 volt drills.

I have used the M12 Milwaukee system in my prop making workshop at home. For many things it works really well... extended run times or heavy work with thick aluminum is a little problematic but for foam, styrene and resin the tools work quite well ( In my other home shop, I use the Dewalt 20 volt system)

I like the versatility of the tools available for the Dewalt 20 volt system
We have angle drills, a 4" angle grinder, a VERY nice jig saw and a variety of lights and things that are very useful in the pit or on the field. They even make a USB charger unit that you use one of the 20 volt batteries for.

We have never had an issue with any Dewalts... and we, like many other teams before VEX and AM, used Dewalt transmissions for a variety of applications on our robots for competition.

I would suggest 2 drills, an angle drill, a jig saw as a start....
I also have a very nice circular saw, and "multi-tool" but that isn't really necessary for robotics work.