I would venture to say, there isn't much difference between the 2011 and 2010, in terms of reliabilty. The only think I can think of, is GM dropped the DVD based NAV in 2010 for a CF card. Which is much better. You will loose the 6 disk changer and tilt screen, which doesn't bother me anyway.
If you can find a 2010 with lower miles and in better condition, I'd take it over the 2011.