Right now the micro trend is the ER, but I don't expect that to continue for long. Historically the 88 has been the fastest all around AC to get a base you want (that has it). With this amount of hiring though, you should probably get it after your first year anyway even if you guess wrong.

If I had to guess right now, I'd guess the 88 then the ER then the 320. Being the plug (or anywhere near) sucks, but it sucks a lot less if you live in base. MSP 320 plugs (the bottom part of the category) love the base and the plane, so the movement out will be slower. Local MSP 88 pilots will probably start to migrate to the ER once the music stops and chairs are pulled away, so the 88 should be easier to get into category, possibly within your first year.

Like I said though, the micro trend, for the brief moment of now, is the ER is the fastest. But that can and probably will change rapidly. Can you sneak in before the music stops? Maybe, and some have. But long term the 88 is the fastest. Either way though, if even half this much hiring continues as retirements pick up even slightly, you shouldn't be a commuter for longer than a year or so regardless.