i would go with the S6. But then again i am just a die-hard android fan. If you order the phone form the company you can try it out for 14 days. and then return it and try the other one if you are unsure which you would like.
Galaxy S6 has a real smooth look and feel to it, where as the Sony is functional waterproof, the S6 isn't ...
this is a going to have to be Sony for me, i have the Z, Z1, Z3, and not im getting the Z5 premium (as soon as the price drops a bit more lol)
Samsung fan all the way. Got a Sony work phone and it seems basic compared to previous Samsungs I've owned and replaced