[sublynx]

I think one thing that was not mentioned yet, is the time available for playing the game. With a VII you sail to your grid in a couple of days, spend all your torpedoes on a couple of convoy attacks, possibly in one day and sail back to your port in a couple of days. With a IX you might be sailing over the Atlantic for a week or two, then hunt around for a week or two and sail back for another week or two. I try to use TC 128 in airplane ridden areas and that makes using a IX pretty much impossible for me, especially late in the war where the airplanes are pretty much anywhere. I don't have the RL time for a IX.

Historically IX's were not used in the Mediterranean, so that is one thing that could help choosing. VII is the workhorse that can be used in pretty much everywhere, whereas IX's strengths work best in long range patrols.