On the PK/81, MM/85 thing
I've heard the MM-85 comparison; I dont agree personally. The MM is a sharper and smoother pickup, clearer top end by quite a long way, and as eric says, its less middy and the voicings and characters of the pickups are really very different. They feel really dissimilar to play through too, but thats quite hard to explain, and quite a personal style thing I suppose.
I've occasionally said that the PK is the MOST similar BK to an 81, but that doesnt really mean to say that they sound all that alike. 81s have a really, really strong pick attack and a high mid biased sound with very tight, but not terribly large bass response. The PK shares these characteristics, but its not as compressed and congested sounding, and is much more organic, and not quite as hot.
The C-Bomb is a little darker than a PK, with more low mids, less high mids, and the top end doesnt extend quite as far; its got a sweeter, smoother top end than a PK. It would get about as close to the darker, thicker, smoother more 'modern' sounds you want (like KSE for example), but would struggle with the crunchier, grinder old school thrash stuff (like slayer and pre AJFA metallica) compared to the PK.
