I recently upgraded my S4 to an S7 and I love the S7. I don't know the camera spec differences but I just like Samsung better. Graphics on a phone are what you expect. I doubt Apple and Samsung are very different with that.
My S4 throughout the last year had some serious battery issues, though. I was charging that damn thing 3-4 times a day and if would drain battery while it wasn't even in use. It might have been a battery issue that I could have been able to fix by getting a new battery, but it might have been my outdated phone with their new updates. Either way, I think you experience obsolescence a lot more in an iPhone than you do in a Samsung.