Regarding the performances of the two female protagonists in Whale rider and The New World, I felt both were equally remarkable. The difference is in my opinion in the direction. I found "Whale Rider" full of clich, and Caro's direction very text-book like. As a whole, the film was thus a failure for me. 
It's different with "the new world". Malick may be one of the best living directors, and though "The New World" often felt like a mess - as well as over-constructed, rushed, and clichd - it is not only an unforgettable experience, but imo also one of the best films of 2006. 
What i saw though, was sadly the shorter version. I don't know how much difference 15 minutes can make, but one thing was clear after the screening. The movie was way too short. Malick is known for shooting a lot of material, and I hope it was only commercial consideration that forced him to cut it down. As it is, almost all of the films shortcomings (which aren't few) were imo due to this compression. Hopefully the longer version "eliminates" some of them. 
But despite all my criticism, a beautifully rich and complex film, that is a must see.
We'll probably meet again at the end of the year when writing about the highlights.