Roger, I simply must be watching a different DVD of Captain Blood than you are. While I find the image acceptable, it is not beyond criticism, I'm sorry to say. It has many dupey-looking sections, there are many negative scratches and quite a bit of wear. If you want to directly compare it to one film in the Marx Bros. set, compare it to Duck Soup. I happen to think Duck Soup looks better.
I'm not in any way trying to be argumentative, but I'm sorry, the elements used for Captain Blood, IMO, are wanting - wanting in a way that the elements for The Sea Hawk are not. Just compare those two DVDs, Roger, and tell me there's no difference, that both are equally fine. It's no sin for Captain Blood to not be perfect, if that's the shape the elements are in. If that's the best we can have, then great, I'm thrilled we have it. But to ignore its imperfections makes one wonder, because they're there, no matter how you might like to convince me otherwise.