I want to upgrade my iPhone 5 slate to either a 5s or a 5c but I don't know which one to get?

So the reason I want to upgrade is because of scuff gate, this morning I took out my slate iPhone 5 from My griffin survivor for the first time since I got it 3 years ago, from the first day I had the case prepared to go on the phone the moment I took it out of The box I put it on. Ever since that day I haven't took it out until this morning. When I took it out I was shocked to death. The entire back was full of scuffs, barely able to see any black anodised aluminium I'm disappointed with Apple about this! So which phone should I get? 5c or 5s?

That's far less to do with "scuffgate" and much more to do with you not following the instructions Griffin give to regularly remove the case from the phone to clean out the inevitable debris which works it's way inside the case and then rubs abrasively with every slight movement between the phone and the outer case.

But the 5c is simply your present phone in an inferior quality polycarbonate shell, and the 5s is a significantly upgraded model (it's not functionally much different to a 6) in virtually the same shell your 5 has. Apple may possibly have changed the grade of aluminium alloy used to be a little more scratch resistant or to have harder anodising but my old slate grey 5s still looks pristine after spending a year in my Otterbox protective case. I did remove the case once or twice monthly to thoroughly clean out the inevitable pocket grit and I'm certain that's the reason it still goods really new rather than any improvements in the alloy as mine was an early 5s model before any such manufacturing improvements could be made.