The amount of molasses added to some beet pulp is tiny actually. It wouldn't be an issue for my horses but since BP with molasses added is not available here, it's a moot point.
I think just plain beet pulp is fine as it is. Some manufacturers add molasses to make it more palatable, but my horses devour it plain with no problems. They always have. To answer your question, is it bp w/o molasses better for them? probably, but again, it's not a huge amount.