According to Wikipedia, the 757-200F can haul a 72,210 lb (32,755 kg) payload over 2,935 nmi (5,435 km). Passenger 757-200s have been modified for cargo use as the Special Freighter (SF) and the Precision Converted Freighter (PCF).

Several websites list the A321 P2F as having a max payload of 27 tonnes or roughly 59,525 lb. Wikipedia says, “Over 30 years since launch, the A321 Maximum takeoff weight (MTOW) grew by 20% from the 83t -100 until the 101t A321XLR.”

Most rumors and discussions boards are saying that a factory built A321F would be based on the A321XLR with the higher MTOW, but instead of a 4700 nm range that they’d lower the fuel capacity to increase the max payload.

The 757-200 is 155’ long and the A321XLR is 146’ long. Based on this info any A321 freighter will have less bulk capacity and less payload capacity compared to the 757. The stats are similar, but the 757 is still a better freighter, IMO.