Convoy attack vs Port attack

[Raf1394]

Do you guys prefer the standard convoy attacks in open sea? Or do you guys sometimes try to sneek inside an enemy port and find some good targets.
For example. Trying to sneek in Liverpool or Portsmouth ports, and sink every ship that is docked there.

I just gave British ports as example. But could be other allied ports.

The difficulty is not the same i guess. Ships docked in ports are easy targets. But getting there undetected is a challenge i think. Also consider the shallow waters incase you are detected.