A good friend if mine has the Bosch and doesn't like it. He says that it gets too hot to handle it after extended use . Now, I don't know if it's true, but the dude has always been a honest guy.
I'll throw my vote to the Dewalt. I have made 4 friends of mine buy one from a simple demostration:
Take two drills, one Dewalt Impact, and any other drill you want (non-impact), Now grab a couple of studs and nail them together. Use a 4" deck screw and drive one with the regular drill, one handed, two handed, I don't care. You can't put enough pressure against it to make it not spin on the screw head.
Now grab the impact drill, and only use one hand. Hell, use one hand loosely. The drill will drive that screw in with ease. No stripping, or spinning. In fact if you are not carefull it can and will drive the screw through the board. I swear buy the drill. I use mine at least 4-5 hours a day and it's never skipped a beat.