I do reckon XT is a little bit better made but I far prefer how X9 actually works out on the trails. Never had any bother with reliability, I've gone through a few mech hangers but no mechs, they're both getting on a bit now and feel wobbly and baggy in your hands but they shift fine so I'm not bothered. Both are covered in scrapes too.
Only real gyp I have is that the new ones often seem to have issues shifting into the highest gear on the cassette, the spring seems slightly too weak so sometimes they don't reach the end stop. Leaving the bike in that gear overnight sorts it but it's a bit of a fail. Trivial though.