The 700e from the 1930's drivers are all flanged. I think it needs O-72 curves, but am not 100% sure. The middle drivers on the 6-18005 are blind, so it can run on tighter curves. I think the 700e prefers t-rail track as well due to scale size flanges.
The piston guides on the 6-18005 are not true to the 700e. The factory placed the bottom on on top, and the top on the bottom.
700e:
6-18005:
That being said, I will be buying a 6-18005 someday soon. Something about getting the engine you wanted as a kid that seems satisfying.