I don't like either.
Sloane has a really sludgy sound to it that I just can't stand, it's very heavy and dull. I absolutely don't find it pretty.
Maxine is... every
Maxine I've known has been quite unfeminine, either a tomboy or sort of frumpy. I do know a
Maxine who doesn't go by
Max, so it is possible... but
Max is the only nn that really exists for it, so people are going to want to use it.