I like being able to swap the battery. Back-ups are pretty cheap on Ebay. I also like being able to add an extra memory chip for about a dollar a gig. The customization is also nice. I use the Swift keyboard and love it.
I have an SGSII and before they upgraded my OS a month ago I had an app that would make my phone a hotspot without incurring the hotspot fee (damn you Sprint.) My wife is not as technical as I am and she prefers the Iphone as everything is simpler (dummed down.)
I will upgrade to the latest 4gLTE phone when Sprint rolls it out in OC next Spring - Summer. By then the SGSIV might be out!
On my SGSII there is a feature called SprintID which uses a more Droid pure interface. I like it better than tw. Although I didn't have issues Touchwiz.