Are you a side sleeper? Do plan to use it in the winter/snow, or is it mainly for summer? Is weight more important than comfort, or vice-versa?
I use a thremarest neo-air x-therm and I absolutely love it. Super high R-value for winter, ultra lightweight, and pretty thick and comfy. I've never wanted a different pad, and I LOVE trying new gear, so that's saying something.
The material on the Xlite and I assume the Xtherm does indeed seem light, but it is amazingly durable. My XLite has probably suffered through more than any other inflatable pad I've owned without getting even a small leak. I use an All Season more often lately but only because I prefer the fully rectangular design that the current XLite lacks.