Yes indeed, this is a very personal thing and so testing yourself is the only route to take, if you can.
This is the first I've heard of that back pressure/blow back effect. I've never experienced it.
There is agreement that the main difference is the greater volume of the Micro. The consequence being more air/vapor thru the larger perc and hence cave's "more diffusion". But IIRC the slightly small perc in the Ion is accordingly proportionately tighter, hence the bubbles are smaller hence there is more water contact hence my thought (cheating behind the "possibly" caveat) that the filtration may be better. But it's probably true that the Micro technically does more diffusion - after all, the cave shop is in the business and I'm just one user - but of course the question is to what extent is that meaningful for each particular user?
I will re-emphasize relative to the Micro's large can: I don't have the lungs to white-wall and pull all of that through in one rip without it being a bit uncomfortable; that requires in essence a draw of about 2x the can volume. So I clear the white-wall in a second pull. If I don't white-wall, the second hit will be thin with lots of air. Huge white-wall hits is what the Micro is intended for; IMO the user needs to do that (whether as 1 or 2 hits) to get Mobius's designed-for effect.
Something I didn't think of in my prev reply, is the matter of smoke vs vapor. When the cave shop mentions "more rips between cleanings" in ref to flowers, makes me wonder if they're thinking mostly about (much dirtier) smoking, not vaping. I stopped using a flame ~15 years ago. Vapor, depending on the vaporizer, requires more air to be pulled thru. The difference in the experience is not trivial. I would think that the flame does really bias toward the larger Micro piece, while vapor might change that equation?
For me (and especially my partner) it simply comes down to what is most comfortable. We're not looking for the brain hammering effect that I once got with a flame and a single hit off a large water pipe, like I did in my 20's. If I were, I would def be using the Micro. For us though, the Ion is the "just right" pooridge. Choices are wonderful, good luck on finding yours.
You must post back here the results of your investigation!