I use both. I used to use only north up but started playing around with the heading up mode when I got my new nav system. Going up the Sacramento River to do some sampling, I put one monitor
on North up mode (Nobeltec) and the other on heads up mode (Navnet 3D). I found myself using the north up mode for looking far ahead and the heads up mode for looking at things that are much closer. I do find it a little disorienting sometimes to look at a chart that is upside down in heading up mode. I got pretty much used to that though now.
, I use the heads up mode mostly but sometimes with go to the north up mode depending on the situation. For radar
plotting though you have to use the north up mode to generate a good RML...either that or you have to be an excellent helmsman.
I don't think there is a right or wrong setting....just what you're personal preference is.