I don't really care what sex my gliders will be, but my girlfriend only wants females. She doesn't want them to spray everywhere.

Intact males do have a distinctive odor - but - neutering will get rid of that issue

Males don't spray to mark. :3 They rub their chest and head glands on everything to mark it. Neutering will get rid of the head gland and make them smell less too.

Which one is more playful?

I think that depends on the individual glider, having several different cages I can tell you that in the cage with my trio (2 males 1 female), the males are much more adventurous and playful - but when I get the cage out with just the girls in it - they are both very playful - of all of mine, I'd have to say that my little girl, Bailey, is the most playful - but every suggie is different.

personality varies from glider to glider.
like with humans, it depends on the individual glider

and don't worry about "spraying" their "marking" is nothing like a dog or cat.

They just rub their head and chest on things...it's actually cute...and you feel so loved when he grabs your hand and starts rubbing his head on you.

imo the smell isn't bad at all, but ask my husband and you'll get another answer.

They do not smell that bad. At the end of the week their cage might get a little smelly. But that is when I have to clean it anyways. Males smell musty and their urine is stronger but like everyone said neutering will help that. Out of all of my gliders my females are more friendly and they like to play more. But it just depends on the glider. I like both. They all have their own little things about them that just makes you love them regardless if male or female.

I highly recommend neutering males. I guessing you've never had one mate with your arm? (it's customary for the male to bite the back of the female's neck while mating. some males have been known to be too rough and leave an open wound.)

A lot depends on the individual glider's personality. I have two females and a male. I love all of them, and I love having my little mama's boy! Neutered males don't produce the same strong odor as intact males (their scent glands stop producing as heavily), and they aren't controlled by those hormones either.
When I get more gliders, they're definitely going to be neutered males (at least most of them).