I don't know the GC stuff but from what I have read about it and BitWise, not much is different. BitWise has somewhat a better look to it IMO.
OC is new to me as well. I sell URC mostly and understand both company's programming. Lately I have been getting calls from customers that I have sold them URC and they want pad and phone control of the system. In looking at products i found OC, so I spent time learning the program and for ways of it controlling their lighting.
I also like the fact I can make changes from my office and the customer can sync without me rolling a truck.
Hope that helps.