the dewalt is unstoppable. and its ALOT smoother than my harbor freight grinder. it has like 10 amps. where my HF has about 5 i believe.
we learned alot of stick, i got to mess with a tig machine (and yes i still suck) and we did brazing, oxy-ac. cutting, (i wont bother spelling that....) and the plasma cutter i tried a few times. it was great, the pasma cutter just tore through thin metal WICKED fast. we didnt really go through MIG as much as i hoped.
EDIT: i have heard that the grease in the HF grinder gearbox is crap, and when changed with higher quality grease, it lasts longer and makes less noise. have you tried this? i have a can of pennziol wheel bearing grease sitting around that im sure is better than the chinese crap.