After completing the first real patrol:
Advantages over SH3/GWX:
- very nice danger level display around warships (realtime contact update enabled...)
- automatic ship/convoy route forecast (while plotting waypoints)
- graphics
- U-boot interior (minus the crew zombies, who are terrible)
- reveal hidden ships ability (sound guy). Before SH5, the hydrophone was underpowered (couldn't detect convoys at 100nm).
- >256x time compression apparently doesn't disable aircrafts anymore (in exchange, aircrafts don't ever attack you...)
Disadvantages over SH3/GWX:
- everything else. AI, ship fires, ship damage model, sub damage model, simplified controls, interface, commands. Either non-existing, only SH3-era or even worse.