I have not found many mods that I do NOT like... that is a fun fact for me. You might end up liking one and one only, or none at all. Definitely a personal matter. Before you go much further though, what version of Silent Hunter 4 do you have? That will determine what you can and cannot do with mods.
You will likely want to use JSGME (JoneSoft Generic Mod Enabler) to activate and de-activate the mods you want to experiment with. MultiSH can really help if you just can't decide between a half-dozen mods, and want to have them all active, but in separate game folders. And, if you have a newer computer with a 64-bit OS and over 2 gig of RAM, the LAA (Large Address Aware) program can help get a little more "efficiency" out of the game.
I don't mean to overload you with info before your question is answered, but here's some threads to use for investigation:
Silent Hunter 4 Corruption Management System (SH4CMS)
Make an SH4 lockbox and independent game installations
SH4 <> TUTORIALS <> HOW TO DO IT <> INFO ...