Well I have checked out the video to xenonaughts and while it looks like fun and I know its in alpha but UFO afterlight seems to be miles ahead of it.

The combat system in xenonaughts is very antiquated as is the isometric view.

UFO afterlight has a full 3D environment which you can pan around. Even though its still turn based it is a continual real time motion. So no clicking end turn then waiting for the enemy to make their move. The enemies move in real time with you. Graphically UFO is miles ahaed and I am not sure xenonaughts characters can kneel and go prone, they certainly can in afterlight.

Seriously, if you like this genre, then you are missing out if you don't play afterlight.

If you would like, I can post some pics and a bit of a intro to afterlight.