Hi Guys,
I have some experience with Optech CMS, and the MDL Void Scanner.
In the past we were using the MDL product - the old version of the Void Scanner. I think it was VS-150, and honestly I am not impresed with it. We had serious problems, couple of repairs for an year not because it was hited or something. Plus a lot of incorect models because of the dust in our stopes. I don't know much about the new model of MDL, I know that it is faster, and hope it is stronger.MDL have a good postprocesing software that alows you to filter the data.
After our experience with MDL, now we have two Optech V400 Scanners. I think they are pretty reliable. The models are looking good, the scans are fast - about 7mins for full scan with 1 degree step. One of the scanners was hit by a rock falling from about 30 meters and the result was broken first boom some scratches on the scanner, but it is still working and giving us good results.
I haven't seen Geosight Minei, but have heard good opinions about it.
And as Tim said it is important what do you want to do with the data, and in which software you will process it. And also the onsite demonstration from the diferent companies is the best way to decide what exactly do you need.
Best Regards,