Had a look at getting a spare bottom bracket for my bike. Current one fitted is a Shimano bb71, looking around it would seem that replacements can be had fairly cheap, even what appears to be an xt/xtr one. So is there anything between them? Sealing ,weight or tolerances? I know the differences were few in the past if any. Also is the Shimano unit a decent enough bb? The Hope one seems ££ in comparison. The Shimano one fitted is still working fine, this is only for spares.

I can’t comment on quality. But keep in mind u can also use a “road” BB. I recently bought one and it worked fine. However the spacer part (that fits between the 2 outer bearings) was obviously too short, so I just used the old one. The spacers don’t wear out so they are reusable. I found the road BBs significantly cheaper for exactly the same BB product code.