I like the Megs better. The OPT/CG/ADS microfiber pads don't cut as well, but are a bit easier to use with a rotary because the foam backing is a bit thicker.
Have used both on Flex Machine. Meg's do hold up to the machine at all and I feel that the cut of the OPT. is much better and they run cooler than the Meg's pads.
I really like the OPT MF pads. Have has one compounding pad fail on me because I was being stupid. Lol. Have found the cut to be enough for the jobs I need them for though.