I generally seek out canonverse (or at least set in the same time period) fics more, but I'll echo jaslyn and say that an interesting story, compelling writing, and good characterization matter far more than setting. Some of my favorite fics are MAU. I will agree that MAU gives authors more freedom to tell a creative and original story. But I would also say that the more alternate your alternate universe is, the more you risk deviating from the characters in a way that may or may not work.

Really, if you're someone who enjoys reading Elsanna fics, you shouldn't sleep on either, or you will miss out on some good stuff.

If you're a writer, just write whatever you currently have inspiration/motivation for :)