I would have already done my research regarding construction methods that would work best for my use: insulated(and level); metal vs wood framing; interior finishes such as MDR/plywood veneer cabinets vs solid or mostly wood; interior lighting with LED bulbs vs incandescent; how and with what the electrical system was manufactured and same for the heating and plumbing system.
This would enable me to have a conversation on the mechanical systems without being blinded by stuff like layouts and how pretty the cabinetry/paint finish/wallpaper looks.
I don't see factory reps as having a different end game from salespeople although they are probably more knowledgeable about construction.
Have fun @ Hersey!