There is only 2 P's in a 3.5 inch Soap bar housing offered. The 35P4 & the 35P4X , both with Ceramic Magnets. I have a Geezer in my Butterscotch Model T and It's a great sounding pickup, I was surprised it uses Alnico 5 Magnets. It has a low-mid bump somewhere around 1,000 Hz that give it that Grind/Grit/punch that a lot of us rockers love. I can get an almost Identical sound with the 35P4 by bumping up the graphic EQ at 1,000 Hz. The Geezer P is my second favorite Passive P pickup. My Fav is the Schecter Monster Tone (with Ceramic Bar Magnets and Nickle Carbon pole pieces) that they have reissued when they made the Michael Anthony Signature Bass.
EMG says the 35P4X has more articulation, more like a passive pickup and I quote,
"with a truly vintage tone an feel.. With the EMG X preamp on-board, you get even greater dynamic control and touch sensitivity, much like a passive pickup." I've never tried one but it surely sounds like a good one on paper.
I love what I get with 35P4.
Sorry, I'm probably not helping you to decide.
Good luck