ok, here are some files i just created.
i simply put the sm57 (both versions) in front of the driver of an yamaha hs50m, in a distance of about 10cm.
from there into a rme quadmic, into rme multiface, into cubase.
no eq or fx or anything, just normalized.
i recorded only that one speaker, anything else was turned of, so don't expect a great stereo sound or so, it's just about comparison between both versions.
here's a snapshot of firium, wich shows the difference between the modded and the original version, the modded has a little bit more bottom (keep in mind, that the monitors can't project anything below 40hz) and more air.
the high mids are scooped a little bit.
imo the mod in deed removes a bit of the honky tones the sm57 delivers.
i like it.
sounds:
sm57stock
sm57mod
i can imagine, that for snare, kick, vox and some other applications it can come in handy to have both versions.
have fun