Not having ever used the Windows version, the only two things I can say that I'm missing off the bat are the priority in upgrading and RealBand. The latter can probably be done just as well with a DAW, the former doesn't really leave me hanging--there's still plenty under the hood of 2013 to keep me busy. For what I do, the real tracks for organ trios, or any of the other jazz and blues options are pretty flexible right out of the box, and they sound great on a mac. Pop songs might require an extra step or two.

I find that the Mac version is quite stable and plays nice with all of my hardware, as well as my softsynths. I miss the inability to record even less now that I have a Fishman 3-Play pickup for recording melody and solo lines, over as many choruses as I want.

It sounds like what you're trying to do does not necessarily have to be done with BIAB open and running in a gig setting, even though you've obviously become accustomed to that option. Personally, I'm fine being able to output songs to midi and upload into a DAW; that allows you to do a lot of customizations that you wouldnt' be able to do even on the Windows versions. I know guys who, with or without the aid of BIAB, just make MP3s of their backing tracks and cue those up. It's simple, it sounds as good as you want it to, and it's much easier to carry an emergency backup if your player fails or runs out of power. Running a full version of BIAB in a performance setting, unless it's pedagogical, would seem to carry increased risk of failure. If you take that out of the equation, you might find that the Mac Version is even less limited than you realize.