I'd probably say GT4 but burnout is good if you're feeling dumb(sorry if there is another thread about this so correct me if im wrong,but i have checked)
You are comparing a sim to an arcade game that their style it's "destruction derby". That are very different games. It's like compare a palm to a dog.
I prefear GT4 because the feeling it's near to the real life and that makes me get a fun time.