I asked the same question over Christmastime trying to decided which system to get for my son.
Everybody recommended the 360 over ps3.
The deciding factor for me was that there seemed to be a better selections of games available for the 360.
Sony messed up not making the ps3 compatible with ps2 games (the one version of ps3 that would play ps2 games cost over $900.) I absolutely would have bought a ps3 over a 360 except for this.