It is similar to comparing Rand, Egwene, Elayne and Nynaeve - each has strengths in their particular areas that outstrip the others. It's not so easy, therefore, to determine who is the most powerful or most capable - Nynaeve has done things that the others considered impossible with much less experience, but by the same token, we've seen Elayne and Egwene naturally evolve techniques that they had to teach Nynaeve.