Meas Boogie Triaxis is a very popular preamp, but I found it tedious to dial in a good tone, plus it has one hell of a lag switching from one program to the next.
I never tried the 9150 Zoom, because I had tried other Zoom products and found that all of them were very compressed sounding. So much so that they sounded like they were coming through a long cardboard tube.
The JMP-1 was the best looking Marshall preamp, but not the best sounding IMHO. It was very weak and thin sounding to my ears. Marshall had an earlier one that sounded better, that was the 9000(?)
People who bought the Triaxis or a Marshall preamp were really just paying for the name.
Really, the most popular rack mounted preamps that delivered honest and usable guitar amplifier tones, were the ADA's, Soldano, and Groove Tubes. When I was shopping around for another preamp in the early 90's, I was trying a lot of them out. I found that the ones I liked the most were the Soldano X-77, (SP was the channel switching model, X was the one with the MIDI card in it), The Groove Tubes Trio, (Which could also be upgraded to MIDI channel switching), and the MP-1 Classic.
The Classic had the loudest clean tones and was more affordable, so that made my choice for me. ADA's popularity had dropped considerably by that time because of the MP-2. ( It was too complicated for the simple-minded guitar players). So by that time, the only remaining popular rackmount preamps were the JMP-1, Triaxis, and the Rocktrons.
Up until that point in time, the MP-1 was really the most widely used preamp since it was so versatile and straight-forward, and it was easy to dial in a great amp tone, which you could easily add any effects unit to, to shape your sound the way you wanted it.