Looking at new phone. ..Galaxy S5 or S7?

I currently have a S5 that I've had since they first came out. It works ok, running Marshmallow 6.0.1. It's slow at times and has some lag when I press on things, and the screen glass is coming unglued around the edges. The phone is just heavily used and worn out, I think. I was looking on ebay at new, unlocked phones, and I can get another S5 for about $220, an S7 for about $450. My S5 has 16gb internal and a 32gb micro card. I'm always transferring apps and such to the sd card, and clearing the cache, but still only have 1gb or less free on the internal memory at any given time, so a 32gb internal memory would be nice. I LOVE the fact that I can snap the back off and change the battery, I'm on my 3rd battery. Any of you go from a S5 to S7? I'm curious if there was a big preformance difference and if the battery life was good. I don't want a Galaxy Edge model or an iPhone and have always had Samsung, so I haven't looked at other phones. Is there a better option around the $400 price point that I should consider? It'll live its entire life in an otterbox and I really need it to last 2.5 years or so. I hate buying phones.

Thanks!