I went with the S7 Edge over the S7 for the following reasons:
Bigger screen
Bigger battery
Those really are the main reasons why. It also doesn't hurt that the Edge looks amazing with its curved screen, and that the curves on the screen and back glass make it feel smaller than it is in hand from a usability standpoint.
The only problem I had at first with the curved screen on the S7 Edge was that I kept bumping icons and links that were at the edge of the screen just from holding the phone. I would also bump keys when typing. I had these same issues the few times I tried the S6 Edge and the S6 Edge Plus as well. Putting a case on it fixed both of those issues immediately, and there are tons of cases out there to choose from already. I'm a fan of the Spigen Slim Armor cases, so that's what I have on my S7 Edge. I'm waiting on Diztronic to release their TPU case as they make the best out there in my option, but Spigen's Rugged Armor TPU is also a great choice if you want a thinner case.