2012 Mac mini vs 2011 Macbook pro for audio postproduction

The FUD spread around the GPU of the 2012 mini is .. well, simply that.
It may not be top of its class, but it's still a decent performer. It's not made of cheese. It's not worse than a GPU from 3 years ago.

Yes, you can play video while using audio software! You can drive two external monitors. (Some say three, but that might be pushing it.) You can play ... games!!

OK, if you're doing video rendering or protein molecule folding, then it's going to be 3 times slower than a new dedicated GPU -- but it's not going to collapse in a heap of not coping.

The i7 CPU is massively powerful, you're not going to be short on power. I use Logic and it's not remotely troubled by it. All those cores means it's not going to choke for anything.

I've got the 2.6 i7 mini with Fusion drive and 16Gb RAM. I do a variety of things with it: Logic, Finale, Creative Suite, and can have them all on the go at the same time, with varying loads.

If you're into benchmarks, the mini beats many recent quad-core Pros. There are always ways to overload any machine, but I don't think anyone needs to worry about 2012 being "a step back" in any way.

I switched to the 2012 mini 2.6 from a late 2008 MPB 2,53. I am a professional Audio Producer. An average PT session with my MBP took my CPU to around 70-90% usage, all buffers set to maximum and some drops in playback every now and then, especially with more than two oder three instances of Drumagog running.
Same session with the mini: 12-14%. But honestly I can't figure your current MBP couldn't deal with the load in nearly the same way... It seems to me the bottle neck is (or will be) the harddrive, but with SSD or FD I can't see any problems.

*edit*
I would try and put at least current projects that you are working on on to the SSD as well. This will give you a massive boost in performance, especially if you need to read and write large files like HD audio or movie files.