I think the guys didn't understand this fact... EVERYBODY HAVE A PC.
So you can play Minecraft on PC if you want.
So PS3 users can play Minecraft without Xbox 360... I think MS saw that because after the first release Gears and Halo never back to PC... now they are exclusives like PS3 ones.
You buy something that agregates... so PS3 agreegates more to your game life than 360 because a lot of games you can buy in PC.
Of course you need to buy a 360 if you want a Halo, Forza, Gears, etc... if you want these games buy a 360.