There are always lots of comments about some of the actors who had a chance to play multiple parts and how well they differentiated them - predominantly Thayer David, Nancy Barrett and John Karlen.
Jonathan Frid was almost exclusively Barnabas, and except for the "young" Barnabas before the curse, was pretty much the same character throughout. One can see why he was anxious to have a different part.
Other than the physical differences - his hair, dress, etc. that make him seem different from Barnabas, I never previously was so aware of how differently he presented him. Today (yesterday by now!), when he was talking to Catherine, I was suddenly aware of how very different a character Bramwell seemed. His whole attitude and manner of speech were so different from Barnabas - it was really wonderful having a chance to watch him in a different part!