Juggernaut = more low mid focused. It has a very gutteral sound and a very smooth and creamy sort of top end. It has plenty of bite but the pickup is badass and very refined at the same time. It can get plenty of aggression and pick attack but it 'purrs' at the same time. It's like a bodybuilder in a tux.
Better in a brighter guitar with less low end
A-Bomb = Bad mannered in a gritty, ill tempered, and greasy sort of way. It's a lively pickup with more mids and high mids, and a very hairy top end. It is brighter with a lot of grit and pick attack which is really fun. A punk rocker with tattoos, huge cylinder earrings, ripped jeans, converse shoes, studded jacket, wild hair, etc etc.
Better in a darker guitar with big, but not overpowering lows and low mids. I think Painkiller / Rebel Yell are for darker axes that have overpowering lows / low mids.
Depends what you want...