Never flew the 757/767, but...
Never flew the 757/767, but I have many friends who have flown both the 757 and the 321. Without exception, the 757 is preferred.
My old company had the CFMs on the mini-bus....the 321 was underpowered....at 93T (205,000 lb) max takeoff weight....it was a pig.
Many times during summer months, at high gross weights (near 205K lb), the 321 struggled to FL300....of course, after some fuel burn, we could climb a bit. (This was ISA +10 to ISA +15 temps aloft....)
The FBW is great, once you get used to it. And, as far as cockpit comfort and passenger comfort, it's hard to beat a Bus. (My opinion.)
Fly safe,
PantLoad