maybe it has to do that they plug in the amp without adjusting the settings and maybe some freq maybe different and so they hear, for them a better sound.
with my gnx1 it is easy to hear when i plug in a l500 guitar ore a l450 in the same setting.
completely different and adjusting for one sometimes won't help for the other.
(still i am not happy with the l450 set and this is not the pups but what i like to hear ore not.
if i could trade them with l500's ore l280's but in the Netherlands i sometimes think there are few BL fans, nothing to trade and try)