FYI - Mine is a early 2011 40' Bus with Powerglide Chassis and the following are original not corrected:
PS kitchen floor is the metal frame vs plywood.
Water bay is the plastic with additional supports.
It does have DEF.
Switches are multiplex but not spyder or maybe an early version.
AquaHot 450 D
I would recommend buying the newest that will fit your budget simply due to aging of all systems. If like many here and you do your own work then the options are greater.
Other considerations for all years in a used motorhome besides engine & tranny:
Awning fabric for patio & windows
Slide Operation & Condition
Look for rodent damage
Hope you find a gem and enjoy the adventure