A Dorking/CX has the potential to be an awesome meat bird. I've bred a lot of slow broiler meat birds to a Naked Neck rooster (wish I had a dorking rooster!), and have been satisfied with the results in terms of healthy birds, that are solid egg layers and make reasonably sized meat birds -- nothing compared to a true CX, but a huge step up from hatchery "dual purpose" breeds. Their appearance varied between almost all white, to ones with a lot of brown mixed in -- either that's from the rooster, or from some new hampshire red mixed in to the broiler line for fast maturity.
If one of your chicks is a rooster, and you are interested in home-brew meat birds, I would consider keeping it.
If one of your chicks is a rooster, and you are interested in home-brew meat birds, I would consider keeping it.