The C330 is a bit heavier, but has a number of features that I really like, and they really justify the added weight and expense. The automatic cocking of the shutter is great on the C330, the parallax indicator is a blessing, as well as the exposure compensation indicator. The distance scale also makes more sense on the C330.
The only thing about the C330 I'm not fond of is the cold shoe. I'm still trying to figure out the best way to get a flash on there so it points forward.
The first thing I did on the C330 was change the foam on the focusing screen, but that was expected before I bought it. It was a thousand times easier to correct the focus then on the C220.
They're both really great cameras, I just like the C330 better.
My first was a YashicaMat 124G, and that's also a great 6x6 to start with.