MD, they're entirely different pickups - P90's and Franzes (roughly the same thing, really) have two magnets under the coil and steel poles protruding through it, DeArmonds are like a caricature of a Fender pickup - a coil that reads twice the resistance of a typical strat pickup, with magnet poles protruding through it that are easily three times as long, and bigger diameter than the typical fender Rod-magnet-polepiece.
The DeArmonds are very powerful pickups that thanks to the magnetic rod poles have more of a percussive, twangy character not unlike a very overwound telecaster pickup, but bigger, fatter, and bolder.
For all the difference in construction though, if you turn down the tone control a little bit, they're not all thàt different in response from a fat P90 in that they have a similar fat midrange content, and push your amp about as hard.
Clean, into a powerful amp with a lot of headroom, they're wonderful "twang" pickups, and a lot of people associate them with that (Duane Eddy!), but plug them into a smaller amp and turn it up, and it's raunch city - very powerful, midrangey pickups. Bo Diddley's rectangular Gretsch custom had them too - not exactly bright clean twang there!
Not recommended if you play 9's with low slinky action, because those huge magnet poles badly want to "grab" your strings - lotsa string pull with these - actually pure nickel wrap strings tend to sound/work better with these than nickel plated or pure steel wrap strings.
