The difference between the two is similar to a delicate pastry crust that takes some delicate handling (Michele's) but tastes wonderful, and one that is easy to roll, but will be tougher and chewier (MMF).
I've found that Michele's is much easier (at least for me) to smooth around a cake, especially square cakes. It can tear but is a much more tender fondant, and blends into the BC base icing very well, so it seems like part of the icing. I also find the MMF can have a bit of a commercial taste, while the flavorings I add to Michele's come through very well and cleanly. I also prefer the taste of Michele's because I like a "no preservatives" icing.
MMF works well for cookies, or when I have to make a fondant drape, I'll blend 50% MMF into Michele's to get less tearing. I use a MMF-Michele blend when I do my wedding dress cakes for the same reason.
I'm glad this post was started...I'm looking forward to reading others' experiences.