Roger:

In this thread I'm beginning to feel like one of those guy's playing several chess games at the same time!

There are a multitude of answers depending on what you want to achieve. Basically, anything you can do in a midi file on the 7k you can do in a NX file, it's just you can do far more and better in an NX file.

So for the sacrifice of the universal format which will load in your friends yamaha, you can get far better voices and effects on your 7k, something that your friend tries on his yamaha with XG format. The difference in this case is that your friend can't play back NX on his yamaha whereas you can play back XG on your 7k.