Well... it depends, really.
In a game with the "create your own character" shtick I usually create the character that is most pleasing to the eye/I think looks best (which can be either male or female), but this is generally because I don't see self-insert characters as, well, self-inserts most of the time.
Only exception to this has been Awakening and that is mostly just because of the whole marriage thing.
So really it depends on if the marriage mechanic returns or not. If it does I'l probably go Mamui, if not I'll probably go Femui because I like her general design better then Mamui, from what we've seen (it is entirely possible that I might find a different build of Mamui to be a better design then anything Femui has).