I like the atmosphere of the B&W episodes, the B&W added to the gothic gloom, IMO. However, I like the show in color too. So I'd probably vote both.
Many of my favorite episodes are in B&W (the early Barnabas episodes), but there are also many I love in color too (pre -1795, 1795, 1897). I have a hard time imagining some of those storylines in B&W.