Actually would have to second Ariel, since as far as adventures go... she's got this great family and this great place to live, and yet she wants more.
Okay, I did just paraphrase the song, but I guess I see her as a strong heroine because I identify with that - I have a lot of really great things in my life, but it's not just for me. Plus, unlike Belle, she does have to sacrifice something major in order to be truly happy.
That said and done, I think Disney princess films have definitely given me unrealistic expectations about what life and love are supposed to be about. That's why my Disney heroine is Perdita from 101 Dalmatians .. she's got it all.