Mark, I have a #10 but not a #33 to compare. The #10 seems to be reasonably "slippery" in coasting after cutting power though not very much, especially when pulling it's cars.
You are correct in that they have different types of motors, and the difference may account for the additional coasting of the #33. I haven't played with any of the Early Period locos so I have no experience.
Are you running the engines light or pulling a train?