Originally Posted by
hokiefyd
Deore is a few steps above (nicer) than Acera in the Shimano mountain group hierarchy. Having said that, it's hard to know if there will be an actual difference in performance without knowing the part numbers of the derailers.
Anecdotally, I actually prefer the Altus rear derailleur on my 2017 Kona mountain bike to the Deore on my 2014 Fuji hybrid. I don't know whether that's due to the three-year difference in vintage, a random anomaly in production, or what. All I know is that the Altus consistently shifts more smoothly than the Deore. I'm not saying that Altus is better than Deore across the board - just that I don't think the difference is as big as we can sometimes make it out to be when shopping for new bikes. It won't be nearly as high up on my considerations list next time I'm in the market for a new bike.