I get my games from Game and if you don't like it you can return it within 10 days to get a full refund! I've abused their system so much lol!
As both games lack online multiplayer, choose COD if you're a lone gamer or Red Steel if you plan on having mates round.
Personaly, the AI, Camera and clipping in Red Steel would piss me off. I remember buying Rouge Ops for the GC and taking it back the same day because the clipping on the game made is totaly unplayable!