they basic salary is the same, however suppose a 320 pilot and a 340 pilot flew the same number of hours in a month, the 340 pilot would make several hundred dollars more in layover money (and most likely have more days off)
EY wants to eliminate fleet envy by not directly paying more based on the size of the aircraft, which is good, but the 320 fleet invariably flies more due to the shorter segments. The basic pay is good on any fleet, and the main reason most pilots want to transfer is the improved schedule on the widebodies.