I will never understand wrapping aluminum around the iPhone. If you drop it, it gets scratched and dinged, and looks like crap from that point forward. Plus I cannot see how aluminum is going to provide better shock absorption than plastic or rubber.
If you never drop your phone, then there is no need for a case. If you do, then why not get some thing that offers more protection at a fraction of the cost?
Because they aren't stylish. If I wanted the most protective case out there, I'd spend less and get an Otterbox or something similar, but I don't like the bulk or how they look.
I'm not sure about the others, but Element cases have shock absorbing liners. In addition to that, the Sector 5 comes with rash guards for extra protection against scratches.
My 4S took two hard hits while it was in a Vapor Comp and the phone was fine. One was on concrete and the other was on tile. The aluminum Element case, however, got scuffed on the concrete and got a dent from the tile. Overall, I think the case still looked really good. Anyway, other cases get dings and scratches from impact too. That being said, I'm aware they aren't highly protective, but they do provide
some protection.
Also, the Vapor Comp had absolutely no impact on signal strength. I'm not sure about the Sector 5 since I don't have it yet.