The A321 is a great a/c, from the FCOM ISA +20 at MTOW it will reach FL310, depending on the airline config anything from 178 to 220 pax at 3t/hr. The times that I have travelled on the B767/B744 out of Asia they would never be near MTOW but seem to spend a lot of time at low levels on a 9hr trip to OZ, and by the way a QF B767-200 only carries 202 pax burning a lot more fuel.