I've had a similar dilemma bout to buy a ps3 or 360, but ps3 might win for blu ray and the hd digital tuner option.

Playing both at the shop, forza was more realistic but yet easier to play for me. But gt5 has some great tracks. The dynamics are still great if not better but walked away cause I didn't find it as fun to play- was more like a challenge and was a bit tiresome. Forza at least you can do some crazier mods on the cars