I've been running Plex (originally a fork of XBMC) because it has support remote clients (ie, displaying the UI remotely and playing video)

I can start a video on my Samsung TV, stop it, then pick up from where I left it on my Android table (I believe there are iOS client apps too).

That's a killer feature, and I don't think XMBC has it. I'd love to be wrong about that though...