Tina can't play the whole game -- she's solid in spurts but runs out of gas while Emma is at top speed the entire match. I think they compliment each other well as Tina has a nose for the goal, a strong shot, and good one-on-one moves while Emma, although not a technically skilled player, can run for miles and brings energy and enthusiasm to the match. Tina's numbers are down because her conditioning is down from last year. Emma's numbers are down as well but that has more to do with losing last year's seniors.
The main difference between the two (aside from conditioning) is that Tina can create her own shot while Emma relies on others to provide her with opportunities. Althogh she is a great athlete with the God-given skills to play at the next level, unfortunately she has relied on her speed for too long without developing the rest of her game.
So while Tina COULD be the #1 option if she were in better shape, for now Emma is the best we've got. If Kat continues to develop and depending on how good this hotshot recruit we just signed is, these two might find themselves on the bench at the opening whistle next season.