Re: duncans or dimarzios?
well the fred and jb are two completely different pickups for different applications, imo. jb is much hotter and higher output than the fred and seems a tad bit more compressed. the fred has that upper mid boost which lends it to some crazy harmonics, but i've found that i really only like the fred in basswood and mahogony guitars. i've got one in an alder ibanez rt and it sounds kind of lifeless. i haven't had the opportunity to put the jb in basswood or mahogony yet, but i will eventually. jb seems very versatile to me, crisp, articulate and cutting. some people complain about its high end being a tad harsh, but i haven't experienced that (at least not in alder).
and the dimarzios i've heard have been warmer, but warmer can also mean less articulate and sometimes muddy (fred being the exception). i'd like to try a breed though, heard lots of good things about it.
and the statement about duncans working only in cheap guitars and amps is ridiculous and uninformed. both manufacturers make some really good pickups and some that are not so good, depending on what sound you are going for.