I've got a mutt bike that serves as my gravel/winter/light touring bike. It's components are a mix of Deore, LX and XT. The LX long-cage RD recently suffered some misfortune. I was able to straighten it enough to get functional but no where near perfect shifting. I can't find a NOS LX long cage anywhere. What I have found are the current production Deore and XT versions. The XT is roughly twice the price of the Deore but either is within my price range.

My question is, how do the current production Deore and XT 9sp RDs compare to each other and to an approximately 8 year old LX?

The bike isn't a lightweight (27 lb with cro-mo frame) and isn't used for anything competitive so a few grams doesn't make a difference, but smooth, reliable shifting and durability are considerations. I'm willing to spend the extra for the XT but only if there is a significant improvement in performance and/or reliability.