1) less pedal strikes (I lean my bike on corners so this happened a lot with the 175mm)
2) faster exit speed during cornering (i can pedal out of a corners earlier)
3) faster cadence (this def increased and i can get back up to speed earlier)
4) more balance (when pedaling, the side-to-side movement from my hip was reduced)
for me, #1 and #2 were my objectives. it wasn't until using the 165mm crankset for several months that I started to notice that #3 and #4 also improved. i've been using the 165mm since november 25th, 2020 and i prefer them over the 175mm that came with my e-mtb.
also i'm not sure if shimano offers a 160mm crankset for e8000. from what I found on their website, it just says 165, 170, 175