Need For Speed Undercover or Burnout Paradise (PS3)?

I don't know which game to get for my PS3. Which ones better and which one has better graphics? Burnout looks really cool but but the free roam on it doesn't really seem like free roam cos the cars too fast all the time. In NFSUC, it seems better cos you can go cruising and just seems more life like. But i don't know. The races in Burnout look better but the graphics don't look half as good as NSFUC. Please, i need some help....which one do i get!