For me the decision to play mostly NYGM was based on :
1. Instead of having to "spend" renown in order to "buy" equipment - didn't like that from the beginning - the equipment is available at set dates and if I want to upgrade I have to spend time in port for fitting it on the boat (therefore being less at sea)
2. The destroyer patrols scheme
3. My overall "gut feeling" after trying both
I try to play in a realistic way (or should I say what I think is realistic) like I don't man deck guns or flaks myself - don't think Kaptn's did - I don't raid harbours except if on special mission from SH3Gen, I don't use external cams and of course don't reload a save when I'm dead. My "game" is to start in Sept 39 and see how far I can get (from my sig you can see my previous boat U-104 recently died..
)
So from what I have read from the very well done GWX manual (great historical research there) I tend to think I will make a dual install playing my actual combo NYGM 2.3/SH3Gen/SH3Weather/Sailor Steve's sounds 1.4 for this type of gameplay in the Atlantic and play GWX for other types of careers (the Med -sounds great- Black Sea and Far East)
Just my 2 cents and personal point of view, nothing religious in there..
Most important is that each player finds what suits him best even by adding his own personal settings to a few files of a supermod...