Mitch Ryan all the way.
In the first place, I thought his performance was multifaceted. His Burke was a fully-fleshed character--possessed of flaws and virtues alike. I also thought he was the better actor. Even toward the end of his stint, I think he sold the part far better than Anthony George ever did. It's unfortunate that so many fans have not seen his work from the pre-Barnabas episodes because that's where he shone really.
Never liked Anthony George. I don't think he's a particularly good actor; he's competent as Burke, but IMHO, never anything other than that. Whereas Ryan's Burke seemed to be a strong, independent, usually intelligent guy, in George's hands, the character turned into a man who (I've said this before) wants nothing more than to live in a house with plastic siding.
Part of that is probably the fault of the writing, but it was sad to watch a man who once wondered if Vicki was more like "a chocolate malted or champagne" to a guy who was constantly hectoring her for being too dreamy.