One of the beautiful thing about focusing on mature bicycle technologies is that good components can be had at good value for money. Basic bicycle technilogy is very mature.
There is the old Bantrager mantra of “stronger, lighter, cheaper, pick two” and that’s pretty true. The asterisk is that thing gets a lot cheaper in the used market :)
Shimano, the industry pace car
Doddy’s opinions on the Shimano range is a good perspective:
- Shimano XTR vs XT vs SLX vs Deore | MTB Drivetrains Explained!
- Why I Love Deore XT | Doddy’s Love Letter To Shimano - YouTube
So, used XT is on the very right end of the price range in the sweet spot region.
CUES is also worth attention. Sadly (for whatever reason) Shimano did not maintain backward compatability in terms of shift to derailleur pull ratio, but CUES is right in the sweet spot and will be around for decades. So if doing a complete drivetrain replacement, CUES should be considered.
Sride is most interesting
This is a Chinese brand that was doing OEM production for other companies and now moved up to ODM, i.e. they make their own now. Whelp the talent is still there in Foshan, Guangdong and now they call themselves S-Ride. These guys are big into old Shimano and SRAM compatibility.