I have both, non-HD on my phone
and HD on my tablet. I believe the HD is more detailed and also gives you the Sonar Chart option. If you display the HD on a phone's small screen
, in order to distinguish all the detail you would have to zoom in so far as to make the area of coverage not very useful. If you zoom out, you end up with so much clutter on the screen
it is practically useless... Or it scales the detail down to make it useable on a phone display, in which case you essentially have the non-HD version.