I'm no expert but personally I think two girls are best. No neutering required ever. When it comes to temperament of sugar gliders that really just depends on the personality of the glider not the gender.
Some unneutered males fight for dominance. Usually males who grew up together will get along fine. Especially if there is no female in the mix. If you ever decided to get more gliders it can be more difficult to add to a pair of males.
Females tend to be easier to introduce. They aren't as territorial as males making it easier to add to them later if you ever decided to get more.
Of course there will always be exceptions to what I say because all gliders are different and some people have had different experiences. I'm just telling you this based off of the things I've read and some of my experiences.