Running X0 shifters and mechs on my HT and X9 shifters and mechs (with type 2) on the FS.
I haven’t mixed the two as yet.
My experience is that they are near identical in terms of shifting performance, both being instant and positive and reliable. The X0 feels more precise in a clicky positive shift kinda way, the X9 feels smoother.
I have dropped the chain twice with the Type 2 X9 mech, once off the granny and once off the big ring; I’m happy I’ve got the limiter screws set right, so I’m wondering now if the chain is a bit too long. Set up big ring to big sprocket with suspension fully compressed plus one link and the Power Link thing.
If I had the money, I would go X0. As I don’t, X9 is ideal.