Now that is a comparison I am interested in. I own the 2" Baader Zeiss prism diagonal, I have been interested in a BBHS mirror diagonal for years! The more feedback the better!
Looking back in my notes, the first couple of nights were more about finding which eyepieces were a good control group to use in testing. Most of the wide field eyepieces introduced varying amounts of color depending on which diagonal was used, but the false color was brought by the eyepiece, not the objective lens or diagonal. Anyhow, the eyepieces I preferred were the Fujiyama Ortho's & Pentax XW's. The best control group was the ortho's because they did a good job of letting the scope's objective perform up to its capabilities without introducing any variables into the performance.
SVA130T with BBHS MIRROR -
12.5 Fujiyama Ortho - Completely free of false color. Moon was very sharp, as a 2-dimensional object etched in stone. However, the areas near the Terminator were more 3-dimensional. The Southern Polar Region of the Moon almost looked like Stonehenge in black & white. There was also a Grand Canyon look to Clavius. The cliff faces were layered in different shades of gray, sort of like how the walls of the Grand Canyon look in different shades of red-orange.
Issues observed with the mirror diagonal - there was a trivial amount of scattered light towards the Lunar edge. There wasn't a full on halo, but there was a noticeable "shine" to the Lunar surface. There also seemed to be a bigger influence with atmospheric turbulence and/or air currents [or it could just be coincidence]. The image seemed to shimmer more often than with the prism, but again, this could be coincidence.
SVA130T with T2 ZEISS PRISM -
12.5 Fujiyama Ortho - Has a 3-dimensional "prismatic" appearance. The Stonehenge portion at the southern polar region and the Grand Canyon features on Clavius had more depth & dimension. There were boulders scattered about on the walls & floor of Clavius that were overlooked when using the mirror, but they seemed to pop out at you in the prism.
The prism was much better at controlling scattered light. There was a complete cutoff of light at the Lunar edge. There was the bright Lunar surface suspended in the blackness of outer space. There was no "shine" whatsoever. Also, the brightness of the moon wasn't overpowering. You could stare at Lunar features without having to squint to see the detail. Incredible sharpness, as if you were looking at a 4K image on your computer/TV. The image didn't seem to be effected by air currents [could be coincidence*], there was minimal shimmering.
I really wanted to have a couple of sessions in my FC-100DF to see how the results would vary in a different scope, but the last few nights weren't as clear as the they had been the previous few nights. I'll have to try this another time..