It might not have all the fancy features of X0, but SRAM X9 does have a crucial bearing update that makes it the most cost-effective choice in the SRAM shifting arsenal.
So you don’t get the 30 degrees (plus or minus) of angle adjustment on the big lever that you do with X0, but we know very few people who’ve actually used it. You also don’t get the thumbwheel-secured cover of X0 (and the older nine-speed X9) that allows for easy cleaning and cable changes, and that we do miss – this new X9 must be halved by removing all four bolts, just as with the X0 units.
You don’t get a fancy cutaway big lever either, which adds 40g, but then X9 saves you a substantial amount of money over X0, and the rubber cover pops off to let you squirt in some dry lube and pull the cables in and out relatively easy without unbolting anything.
Crucially, a recent update means both shifters now share the same smooth ball bearing internals. This makes shifting a lot lighter than with X7 or X5, and it’s a lot more tolerant of dirty cables than the cheaper sets. That said, they still need more long-term care than the Japanese opposition.