What's better the 2016 camaro SS or a 2016 ford mustang GT also which is more comfortable?

Test drive them both.

You'll have to test drive the to find out which is more comfortable. Seats don't fit everyone the same.

Go to the dealers and test drive them. The one that is most comfortable to me might not be the one for you. Personally, I don't like the limited view out the windows on the Camaro. You can't see what's around you, especially in back. The Mustang isn't much better but at least some better.