WELCOME ABOARD!
There's a third supermod as well - War Ace Campaign.
All three strive to make it more realistic, which doesn't always mean more difficult. An example of this is the old 'Depth Charge' mod, which gave the DCs a smaller kill radius, which meant that they were less likely to do you in, but added the discomforting possibility of undergoing several hours of depth-charging, and still escaping, or getting damaged progressively, which is horrible, or you could still get that one lucky shot that killed you now. All three supermods incorporate something similar, and all three have many similar changes and adjustments.
Other fun improvements include changes in the sensors, so destroyers lose contact with your boat just before they drop. No more 'laser-guided' depth charges. GWX and WAC both have heavily modified harbors, so new and different ships come and go as you are doing the same.
Wilke is right about having multiple installs. Do that and you can try them all for yourself!