XD is another evolution in firearms technology. People are usually either in one camp or the other. Rarely will you find someone who loves both.
I suspect like most others, after shooting both, you'll prefer one over the other. Mostly for ergonomic reasons.
Personally I wouldn't own a gLock. IMO while reliable, they are not as accurate, have crappy triggers (even with upgrades) and feel awful in the hand.
For me the XD is an improvement in all areas over the gLock. Including reliability.