Just home mechanics for me, so mostly just lug nuts and the odd spark plug gets torqued. I use 3/8" drive 100 ft.lb. and 1/2" drive 250 ft.lb. wrenches.
Given a choice I'd probably want a 150 ft.lb. 1/2" drive wrench, which would handle lug nuts very well, and a 3/8" drive with around 40 ft.lb. to handle most other jobs, as my first two choices to own, as they'd be more matched to the jobs I use them for.