Just to balance Ken out (ha!) I'll lobby for the M60. Alan Lofft is on record saying that the M60 has a similar tonal character to the M80. Apparently, the M3, M40 and M50 are similar to each other, and somewhat different from the other Axiom models. Most discussion around here seems to center on the M60 as the model of choice; obviously, I don't know whether that is because they are more popular, or because M60 owners seem to gravitate towards the forums in greater proportion.
That would be a very valuable review, IMO.
