Damn, I have pretty much the same question. I have C4s, and am wondering if it would be worth it to get some C1s for different situations. After doing some research it appears that it's probably not worth it. If I was gonna do it, I would save up the money and go with the C3s. The C1s are just cardoid, the C3s have 3 switchable patterns.
I heard a tape of the Goran Ivanovic Group by mmmatt. It had the C1s on stage in the center and the C4 omnis at the stage corners for ambience and that sound was AMAZING! If I had the set up, and connections with bands/clubs, to do this type of thing I would do it in a heartbeat, but for normal feild recording I am starting to understand that small studio condensers are the way to go.
Anyone who is more experienced or knowledgable than me agree or disagree? I would love to know if I have come to a legitimate conclusion.
Thanks,
Joe