With a mule you still have to have a horse mare, they won't cross water with out a mare to follow.
Mule shoes are harder to find.
What ever you buy, make sure they are raised in the rocks, that's how they learn to put their feet.
I've seen and used some great mules in my life, even ones you could shoot off of. I had some great horses also, you just have to understand the limitations and be ready for them.
