Didn't a thread like this just get closed...oh yeah.
Listen, it's already been made clear what's happening.
1) MS and the XNA is the only stable set-up able to support this kind of community driven developement. Neither Sony or Nintendo have something like this available.
2) Because of this, the artists will be developing songs centered around the existing XNA platform, and therefore will be native to the 360 when they are complete.
3) Due to licensing fees, it would be impractical to demand artists to develope for all three consoles simultaneous. (HMX appears to be eating the costs involved with translating those songs that do cross over)
It has nothing to do with favorite consoles, and everything to do with MS already having the tools available to make this possible. If Sony or Nintendo can release something simliar to the XNA then I'm sure HMX would LOVE to try and get people developing for whichever consoles they're most familiar with.