I would go with the PS3 based on the Blu-Ray offering so much more potential.

For example Resistance 2 (First Person Shooter) aside from it's single player campaign it will have an 8 player co-op campaign (separate story, so you might visit different locations than in the single player game, with different classes to play as), plus the multiplayer maps will allow up to 60 players.

Resistance 2 is expected to be on a dual layer disc which holds up to 50gbs of data.