Ahoy Karl,
As Kenny said....both are great models.
The VII-C was the basic workhorse of the Kriegsmarine.
The VII-C/41 was an upgrade of the C variant and being a boat that saw
much action in the Atlantic later in the war when the Allies air patrols were
hunting them down, the tower was modified and armament upgraded.
So if your looking for a boat with firepower....the C/41 might be the way
to go.
Cheers,
Joe 
