Played with a VIIc so far and liked it best:
Faster when it comes to under water (agility and speed)
the smaller torp load is not the problem imho
the IX was always
-too big
- too slow (under water)
- too long patrols
But as said above... I will give it a try now in my second GWX career (the first one was ended by a fatal windows crash and the loss of a whole partition

)
So I started (after I installed EVERYTHING again) my second career in '42 with a IXc and will see :hmm:
Both boats are good its just a matter what you want from wour boat.
If you want to be fast and sneaky under water I suggest you stick with your VII as the IX really is much bigger and more like a buss
But when it comes to firepower the IX is well equiped to rip a whole convoy to pieces

(once you have shot the DDs

)