Why do Xbox 360 games sell so much better than PS3 world-wide?

[Gamecube]

the2real4mafol said:

foodfather said:

The attach rate is marginally higher on 360, but this late in the gen, most people have PS3 and Xbox 360. the majority of multiplatform owners will naturally opt for 360 because of gamerscore, XBLA friends, better controller and better online, such is pretty much the case with everybody I know.

Why would people buy a game for gamerscore? There has to be a better reason than that to buy a multiplatform game on Xbox over PS3 or other formats. I like earning trophies but they would never make me buy a game just for that. They aren't anything serious i don't think.  

Alot of people have both consoles. Since most multiplats are identical, you would need a reason or toss coin to decide which version to buy. For some people it's preferred controller, others it might be trophy/acheivements.