Is there really this big a difference between AMD and NVIDIA?
Is there really this big a difference?


Yes.


  As on many websites it says AMD is so much better for mining while because NVIDIA has Cuda everyone says its best for editing why doesn't cuda drive up Mhash/s?


CUDA's a software framework for making GPU-based software eaiser to write. More stuff supports NVIDIA cards. Bitcoin GPU miners support both, so CUDA doesn't matter.