GIRLS RULE BOYS DROOOOOOOOOOL! Seriously though I don't know, my torts are all babies and I just give them all silly names right now. Maybe some of the more experienced tort keepers will chime in here?
If kept solitary it really doesn't matter. When you keep them together(both sexes) that's when females can be more favored than males. Males can get aggressive, and so can females. Especially Russians.
Keeping just a single animal. You won't really see much territorial behavior and aggression in either or sex unless kept with another one of same or opposite sex.
I'm a little biased, becuase I LOVE my boy russian... but my girl slucata is awesome too! I'm not really sure it matters unless you're planning on breeding them, or housing them together. Females do better then males in 2-3 groups