Pros and cons of both have been posted. I like NESBA with the exception of the speed disparity in my class (permanent Intermediate). But that's going to happen to any organization running three classes, where you have the person begging and trying to get out of Intermediate along with those that just crept their way into it.
But... having ridden with both (and being friends with a lot of NESBA CRs) I think the amount of attention and instruction you can get from the NESBA crowd is a little better. And lord knows if they find out I said that I'll never hear the end of it