I bought this and replace the bearings when needed!
I believe they’re the same as Superstar’s which is cheaper but I could be wrong!
I thought the numbers on Shimano’s just represent the level of quality so bb71=Deore/SLX and bb91=XT/R. Could be wrong on this but as long as you have 89.5 or 92mm bb then either should fit and you could run the SLX crank.
As for reliability – I think they’re all c**p.
Hope do a £90 one and CK reportedly have one coming out.
Jay