I'm surprised there haven't been more posts to your questions. It caught my curiosity so I went to both websites. There is nothing on the Haulmark site that shows or explains how the coach is constructed. I looked at the various models and could not find any information. On the Showhauler site they explain how their coach is constructed >>> Full Steel Welded Cage. Unless you can find something different I would go with the Showhauler, NO IF AND'S OR BUT'S.
FYI, I own a 2002 Windsor that has a full steel cage, it is solid as a rock and the additional weight makes it drive smooth and easy.
2002 Monaco Windsor 38 PKD
2005 Jeep Grand Cherokee w/5.7 Hemi