I think real good freshmen are better than average seniors.
I think focused juniors are often better for the roster than seniors who are thinking about prom, spring break, class trip, graduation, college, missing my friends (OMG!) come mid-April.
Experience? Most high-level club girls who comprise the competitive high school rosters have been playing in tournament championships and state cup finals and semi-finals since they were nine years old.
In my opinion, that's enough experience.