My 2 cents for what it's worth, and this coming from someone who has not tried NYGM, only GWX and lately LSH.
I think all of the mega mods will present you with a vastly different game than what you've played. I don't have nor can I point you to a really detailed feature list that you haven't already seen in these forums or on sites like
http://www.thegreywolves.com/gwx3/.
I found GWX to be challenging, in just about every way and sometimes maybe more so than necessary, but extremely enjoyable. I'd recommend it based on my experience with it. You won't be disappointed, and as I said, any of these mods will present you with something that feels like a brand new game.
I'm finding LSH to be enjoyable as well, but it's too early for me to make a real comparison.
The best advice I can give is pull down the one that sounds the most entertaining based on the info available. Also pull down one of the amazing GUI mods that have been produced, and experience it for yourself. Backup your SH3 folder before installing any addons, and that way if you end up with something you don't like, delete it, restore the backup, and try a new one.
If you're a true diehard, which it sounds like you may be, you're going to end up trying them all anyway over time, so just pick one to start with.
http://www.subsim.com/radioroom/show...=202719&page=2