Being a photography oriented user, I'm leaning towards the S5. I don't love the design, but the durability and access to the battery and sdcard have me interested. 
I like that it can theoritically be dropped in shallow water without immediate demise. 
I'm not convinced there is a perfect phone on any platform. 
The Moto x looks interesting but the camera and battery would be a huge issue for me. Either need a great battery or an interchangeable battery I can get to myself. 
To be fair, just about any phone would be an upgrade over my 4s. Been a damn sturdy phone, just a bit dated at this point.