Thanks for the response, and the interesting counterquestion.

I think you'll want to 3bet hands that play better postflop against a guy who flats 3bets. So if he flats more so than 4bets, you should 3bet some hands like KTs, T8s, hands that can flop flush and straight draws, in addition to pairs. Your value range should probably be narrower because his 4bet range is stronger.

Against a guy that 4bets and folds more often, you can 3bet pretty much any weak hands (T3s or whatever) because you're probably playing for stacks anyways. Your 3/5bet value range should be wider, since his 4betting range is wider.