BigWalleye,
Both super mods are are excellent in their own right. I have been using GWX through its evolving versions since about 2007...obviously I love it. I recently used Multish3 so I could also try out NYGM, but I am not far enough along in it to give an intelligent opinion. I would recommend downloading both super mods and reading through the excellent PDF manuals included with both....I believe that the manuals will answer all your questions.
Also take a look at Hsie's and Stiebler's patches for the SH3.exec....they fix a few problems and add quite a bit to the SH3 experience.
http://www.subsim.com/radioroom/showthread.php?t=174225
http://www.subsim.com/radioroom/show...highlight=hsie
An external program that most, including myself, consider a must have for SH3 is SH3Commander:
http://www.subsim.com/radioroom/show...t=sh3commander
There are more, but you can get to them down the road a ways.
Kelly621