bump..update
I have both (used) via Guitar Center and taking advantage of returning the one I don't want without penalty, except shipping from one GC to my local branch. The reason I'm looking at these specific preamps is because of the sweepable parametric mid control available on both. My bass has a strong "boxy" mid component (Realist Soundclip, Spirocore Weichs) that needs to be tamed. The standard frequency centers of the amplifiers I have don't quite center on the problem and I need the ability to fine tune the center frequency a bit.
I tried the PZ-Pre (2 channel) on a gig through 2 amplifiers. An old AI Contra and a Gallien MB150. I was quickly able to dial in a reasonable tone with the mid control and look forward to further fine tuning of the sound in the future. Using the 2 amplifiers, it becomes obvious that the basic sound of each amp with the eqs set "flat" are different animals. The sweepable mid of the PZ-Pre allows me to compensate for the difference; as well as the characteristics of different rooms. It's not a perfect solution, but I feel much better about my sound on stage.
Several things for consideration.
1. With two channels, the PZ allowed me to add a microphone (SM57 centered in the bridge using foam) through a ART MP preamp fed into CH2. The preamp is set to mix mode and allows me to blend the two sources should I choose to gig in that configuration. It also allows you to double with another instrument. I use the built in volume pot of the Realist Sound Clip to help with fine tuning the mix without having to access the pedal on the floor once the overall mix between the pickup and the mic is established. A PZ-Pre and the ART preamp, won't take to much room on a pedal board made to hold just those two items. (I don't want to carry any more than I have to. If I had the choice I wouldn't do this at all!)
2. The overall mute switch is useful.
3. The knobs are easy to access on the PZ-Pre. On the Fishman Platinum Pro, some of the knobs, such as the mid frequency pot, is shorter than the rest. I find that the lower profile of these knobs make it harder to access the controls in the middle of the gig. The switches that control some of the functions are also small and it takes more effort than I'd like to be able to quickly access the features during adjustments at the gig. In my case, I didn't need to go further for comparison. I put the Fishman away and decided to return it.
There are many other features which both preamps share and some that they don't. In my case, for the reasons mentioned above, the PZ-Pre is the right choice.