I "upgraded" from 11 speed XT to Advent X on the my full squish a couple years back and for the most part it has been great. I did it for the range but also the aluminum X cassette is pretty light compared to 12 speed or 11 speed parts unless you spend big bucks, and I just wanted to try it. I'm on my 3rd chain and I'd say the aluminum cassette is done and it does get mad sometimes if I try to grab too many gears under load. My hardtail is running 11 speed deore 5100 with an XT shifter and yeah it is a smoothing especially under load but again worn out cassette. I have a cheap light chinese 11-50 10 speed cassette ready to go as soon as this current chain wears out to try.