SE/30 every time! I had a Plus, years ago, but I lent it to someone and now I can't remember who. No matter, because I still have my SE/30. I recapped it myself, messily, but it works now - which is a considerable step up from the simasi'ing mess that I hauled out of the loft during a clear up. Mine has 16MB RAM, a 2GB hard disk, Ethernet and A/UX 3.01 installed. It also has a nifty black back to live in. For SE/30 perfection, all I need now is a Dougg3 IIsi ROM - and then A/UX will be able to use all the installed RAM, instead of running out at 8MB. Would I swap it for a Mac Plus? No. Not a chance!
My biggest difficulty, in installing A/UX, was that my external Apple CD ROM drive is dead - luckily, though, my Quadra 650 lives. I swapped the SE/30 hard drive into the Quadra, installed A/UX, put it back into the SE/30 and Hey Presto! Result!