Not sure why the 360 boost is a surprise FPS games all ways sell better on the 360 compare UK numbers for instance.
FPS game
Bordalands 2 - 360 - 139,498
Bordalands 2 - PS3 - 43,614
Soccer game
Pro Evolution Soccer 2013 - 360 - 11,168
Pro Evolution Soccer 2013 - PS3 - 22,698
Racing game
F1 2012 - 360 - 31,415
F1 2012 - PS3 - 26,364
The sales show that 360 owners are far more interested in the FPS genre in comparison to other genres than PS3 owners.