Hi mate,
Congrats on the purchase
TKechnically the bikes are the same, same frame, engine, seat, weight, tank, etc. I have personally never ridden an X but the R is very nice and comfortable in town as well as on the motorway. I presume the x is more stable in high speeds if you are in that type of thing.
Here is the comparison chart
http://www.xt660.com/site/node/40
Hope this helps
Enjoy