Kojima - Porting MGS4 to 360 would be difficult because the game was developed and optimized for the PS3.
MGS:R - From what I understand is using a new engine built from scratch.
This leads me to assume that it's just easier to make a new engine for PS3/360/PC than to rework an engine made specifically for the PS3 to work on the 360, or the other way around.
4 ≈ One







