I use a corded one, but have used the cordless one somebody gave my Dad as a gift. Doing anything that requires some time, the cordless one's power seems to fall off. I'll stick with the corded one.

I use a cordless driver though - a 3v Lithium and its amazing. I've had it over a year, use it all the time and only charged it twice. There is no speed or torque difference with it fresh off charge stand or using it for couple of months.

Mine is corded, but I think I need to invest in a cordless. Twice this summer at the track I noticed I had stripped screws and I had to go ask the guy who brings a dremel and a generator if I could borrow it.
For a primary dremel, I would say corded is the only way to go, for a travel, or light use, cordless should work. If I have any issues with the cordless (once I buy it) I will let you know.

Sounds like you need some decent wrenches... I've never stripped a screw

corded. i have had both and every one is right it dies fast and wen you apply power to the bit by using it to keep the speed up it drains the battery quickly. I use a roto zip with a 3ft flexable shaft that acts like a flexable dremal tool only it had a tad more power.

I don't know if it is a low quality wrench or low quality screws but I am a pro at stripping the allen wrench heads on countersunk screws (of course only when I am in a hurry to replace something).