there is a reason that 90+% have the same basic set up, intake from front and sides. exhaust from rear and top.
as far as whats more important, exhuast is. if you only had one exhaust fan, it would still pull air into your case while expelling the hot exhaust. all this talk of positive air pressure inside your case is crazy.
in the end, its your case/set up, so what you want. but if you dont exhaust out the rear and top, you will more than likely over heat, and be back on here asking what you did wrong.