From my experience the only reason to changeout the Hop Unit is for ease of adjustment as the Maple Leaf has a wheel on the bottom rather than having to take the barrel out.
Only real "upgrade" (if already using .4g BB) I feel is the steel trigger locater. Even when it comes to the Co2 nozzle it seems to be more fragile, gone through over 50 Co3 bulbs on the standard nozzle where as the Co2 nozzle loading arm broke off after about 5 mags.