I've tried both the XA and the S61, S61 all the way. I just think it has a much better feel to it and more option. In all honesty, many saw, and I agree, that the XA is nothing like the new X series and is actually a step down from the S.
If you're just using the Xa for the sounds you might as well get the XR and a midi controller. I wanted the Xa in the pass, but I came up with a better idea and decide to get the rack so I can save space and because I only need one key of keys. The Xa is good though but it seems like the XR with just keys. Well, that's what it really is right? Hmmmmmm!