I am pretty sure everyones going to Toyota for many good business reasons: Toyota can turn out larger supplies faster, and like you said most likely cheaper (I bet). I am pretty sure they looked over at Honda's system as well, but I don't think it's realistic for them to go to Honda (being the size they are). Nissan and Honda are too close in competition to really work with each other. Since Toyota is big anyway, it won't hurt Nissan or similar size companies to work with them.

I don't know if they are better, but at the end of the day, no one is sure if Honda Civic hybrid or the Prius is (slightly) better anyway. It doesn't really matter.