As I mentioned, my personal machines are the Max units, however the ones that are normally handed out are the Pros. I've not had the chance to work on the M4 Pro as yet, but the biggest difference I've experienced between the M3 P and the M3 Pro Max wasn't one of outright performance, it was one of scale.
My Max for example I'll often have a VM or two running, with perhaps some video exporting in the background and the like. It handles that really well - when I've tried similar on the Pros it's not anything like as fluid.
The performance gains seem to be for scaling out in terms of tasks rather than scaling upward in terms of raw performance - certainly in my general perception of usage anyway. To be clear, my M3M did export video faster than the Pros, but in reality that's not that important (to me anyway). Being able to leave stuff completing while getting on with other stuff though *without really noticing it's doing it* is pretty glorious.
Suspect in reality I'd have been happy with a Pro rather than the Max but then it's not a huge price difference for me (company bought etc.).
*Edited to add, annoyingly I can't use my student discount *and* our business account discount on the same purchase now. Seems they've caught on to that.