Why is it....
We can talk humbuckers, and folks are all over the place, and recognize easily that there are PAFs, shredder's, and all manner of tastes in between. But when it comes to P90's (or the fallicy of P90 in a HB package), folks think they are all real close to the same.
Gibson, has always "marketed" only one P90 (as opposed to marketing many HB pickups), but they've been all over the map in term of winding and tone, and magnetics, and tone, and construction, and tone.
P90's of the long past, as used in the hollow body guitars were rather sweetly wound, much lighter than todays P90. Think in terms of alnico-5 magnets and windings well under 8k, much closer to 7k. This is how it was until the HB came along, with the exception that other magnets were used right at the end of the P90 era. From that point, the P90 was relegated to being "the cheep pickup" for low end guitars, and the windings increased. The windings increased because the pickups were used in brighter solid body guitars, and because in many instances, they were used as the only pickup, in the bridge position. During this time, you get some real whopper P90's out there. My friend voxman/hank has purchased original P90's (not rewound) that have gone well over 10k on the windings, maybe even 11.5k (memory is short here). Gibson also experimented with ceramic magnets during this time.
The resurgence of interest in the P90 brought some changes, with a return to the alnico-5 manget and windings just over 8k as being standard the recent modern past. However, Gibson is up to its old tricks again - the P90 is now close to 9k (or just over) windings and is being made that way for the LesPaul BFG guitar (being hailed as a headbanger's delight).
Having said all that -
I've tried the Phat Cat, P94 Gibson, the Bastard, and the Fat Bastard, all "P90's" in a HB package. None sound like a P90 of any type. Reason is, the P90 has a very low, and very wide coil. The shape of the coil makes a difference. Old radiomen know this, and the quality factor (Q) of the circuit is much dependent on the coil shape. Hence they would wind low wide coils, or tall skinny coils or "square" coils as fat as they were tall. Whats going on here, is how sharp the resonant peak of the circuit is. This cannot be duplicated using a coil of different physical form.
The Phat's are what I call a very "musical" pickup. They do it all pretty well, and nothing great. Real middle of the road - but remember - they were made for the Hamer semi-hollow body guitars. They sound great in those (and similar like a Tele Thinline). Get them in a Strat... less phat (but much phatter than a Fender SC pickup). I have a pair of Phats in a Gibson ES-333 and they're GREAT there. The guitar doesn't shred or do huge overdrive well, but if you need to get on stage and pick out some song, they're there for you with the tone. Amazingly - and I dont know why - the tone controls seem more effective and less stacked-up with the Phats.
I had my go-round with RioGrande. Quality issues aside, I was able to get a Bastard and FatBastard, and both sounded like total crap. Lack of brilliance. I know Jack love's them, and maybe if I hadn't tried the others first... I'd have been more impressed. They were probably ok for some sort of Tejas-Bluz in an overdriven amp, being really middy. Just... a one trick pony perhaps. I tried them in a Tele Thinline, and was not impressed.
The Gibson P94 is one I tried a few of in the 90's. They were (and I hope still are) very close to the P90 "middle of the road" winding. Very strong, aggressive in a solid body, and while having a lot of mids, they dont lose the brilliance either. They do look a bit funny with the "demi covers", but those can be replaced with no-hole covers if you really need to have the looks. I tried these with another Tele Thinline (no F hole) and loved them! But took 'em out because I simply could not find a bridge pickup that was anywhere close to being powerful enough to keep up with the P94. They're louder than many HB's (as also are the P90s themselves)
So... it depends on your musical style, your guitar's body type and wood, and your expectations.
