This really depends on the circumstances, IMO. but the answer remains the same for me. If you've faithfully rotated your tires, the fronts will be the first to fall below the wear bars and need to be replaced. It only makes sense at that point (if you're only buying 2 tires) to put the new ones on the front, and continue rotating when the front wear catches up with the rear.
If I was replacing two tires because one or two were destroyed by a road hazard, I'd still put the new tires on the front for the same reason...so the wear will eventually even out. If you're at all concerned at all about maintaining your tires, you're eventually going to rotate them anyway, so why not start out with the good tread on the front and let them start evening out as soon as possible?
RWD cars can be different, depending on the car and the driving habits. My sister's '79 Mustang wore out the fronts first, because she cornered like a maniac, but the car didn't have enough power to put much wear on the rears. My friend's '12 G37 coupe wears out the rears first because she's a lead-foot. Just pretending for a moment that the G-37's tires could be rotated (they can't due to the stagger), I'd put the new ones on the rear of the G37 and start rotating when the wear started to even out from front to back. But in the case of the Mustang, I'd put the new ones on the front and start rotating.