I have a full body protection on my S6, the one that you spray soap water on the film(military level quality, they say). I had it on my nexus quite while back and this was only option on my S6 and I am quite happy with it.
Tempered glass is good, but there is none that actually cover edge to edge screen on S6 without hollowing effect. It makes it ugly. With tempered glass on the back, it became quite bulky and double ugly. I wasted 4 tempered glass in the end.
Applying the film (mine is a Armorsuit) is quite hard and took me about 30~40 mins. Tip- use hair dryer for the sides. It is not a shock proof like tempered glass, so if you drop your phone your phone screen might crack or the body might dent. But it is quite scratch proof that suits me quite well.