FWIW, I've spent the last 3 weeks going hard on rebuilding the entire website, which will go live tomorrow, and in one of the pages I've been writing over the last two days, I'll have brief tonal descriptions of all mics, cabs, and speakers for those who may not be familiar with any of the particular pieces. There's quite a bit to it, and I literally have about a dozen simultaneous OwnHammer related development projects going on right now, so I don't know that I'll finish it in the next week or so. Being brief to provide some quick info:
FatHead - It's fat, big low end, and where I have it placed also brings out a little bit of chime for it being a ribbon if you have the right pickup/amp/cab/speaker.
Heil PR-30 - Very little on the bottom, highly pushed in the upper mids.
MA-200 - Very balanced and even.
e906 - More even than a 57, with bigger lows and a tiny little spike towards the upper upper mids / lower highs.
MD421 - Extended bottom and top, and of all the mics has a tendency to react differently on different cabs / speakers. Cabs / speakers where the high end is more accented it will end up pretty bright; cabs / speakers where the low end is thick and full it will allow that to override much of the highs.
The rest of the guys here may want to chime in with their opinions and practical applications of these for use with the various Axe amps and their experiences/patches though!