There are zero cube based ATX cases - that's the problem. Most current mATX cases technically have the physical dimensions capable of housing an ATX board. Main argument for ATX in a cube is flexibility, aesthetics (everyone has a tower) and portability. I will agree with you that at least for intel, the past two generations of boards have caught up with ATX, although mATX owners had to wait longer for the boards, just like always.as to the atx vs matx, im a little curious why its even being brought up. this is the small form factor forum, for computers that are small in (you guessed it!) form factor! plenty of great mid towers out there that arent a whole lot bigger than some of the SFF cases, but if size is your issue, i think matx has reached the point where there is little to no difference between them and their larger cousins except expansion slots.
Anyway, mattinv already made his position clear on ATX for his case, so I wouldn't badger him about it.