I own both and don't play FPS either.
WRPGs: Xbox 360
Action Adventures: PS3
As the PS3 has the better library of action adventures, let's have a look at WRPGs:
The Witcher 2, Mass Effect 1, Fable 2, Fable 3, Divinity II: The Dragon Knight Saga, Two Worlds, Risen
=> these are all the X360 WRPGs not available on PS3 afaik (plus: Skyrim seems to be superior on X360)
If you don't absolutely want several of those and if you really want to buy only one console, I recommend you to get a PS3.
But I'd get both consoles at this stage of the console gen. If I didn't already own both consoles I'd get a PS3 just for - say - Flower, Valkyria Chronicles and Uncharted trilogy and a 360 just for Mass Effect trilogy, The Witcher 2 and the superior console version of Skyrim.
