Hi Garth,
It is a nice dilemma to have for sure!
In terms of portability, Mach1, MYT and GM1000 are the lightest and all three can handle 130mm refractor or 250mm RC for imaging, but unguided could possibly be only done with GM1000. I got Mach1 because I wanted portability and reliability and have not looked back.
If I had the money though and wanted to get the best possible data with a 250mm reflector, I would get 1100 GT with encoders or DDM85. While heavier than the other three mounts, you could mount both 250mm reflector and 130mm refractor at once if you wanted to. I also believe that a quality mount with a greater capacity is going to consistently guide more accurately in a range of conditions than a quality mount with a lesser capacity.
From what I understand, unguided imaging apart from a superb mount require a mechanically very sturdy telescope as well, and such telescopes are not cheap neither.