The 3.8 is defintely a lot smoother and better for tooling around town, but they normally also have EDC which is insanely expensive to fix when it goes.
I personally love the raw power delivery from 3.6, and the shorter gearing makes it a tad bit quicker as well, although it would be nice to have a 6th gear on the highway.
It all depends what you are looking for, personally narrow-snouted and 3.6L is what I prefer. Good luck in your choice and don't have too much fun