There are a few related discussions in the forums. Here’s the first that I found:
Generally my thinking is that TaskPaper is more polished Mac app and best for making lists. But if you want to compose documents (instead of just make list) FoldingText is of course much better, since it is based on the fairly expansive and expressive Markdown format.
Also, going forward FoldingText is developed by @mutahhir, separate from me and Hog Bay Software. I’m a cheerleader for FoldingText now, but don’t play any part on it’s development/marketing/etc.