So, I went to the DMV this morning to get my bike registered and what not. Talked to the girl about the OHV decal. She gave me a form to fill out. On said form I had to "certify" that the vehicle was primarily for offroad use. I asked her what that meant.
She says "here's the deal. You DO NOT have to have an OHV decal for Dual Sport motorcycles. It's not legally required. However, Arizona Game and Fish and Sheriff's officers will often ticket people riding dual sports off-highway, even on maintained roads. You will win in court, everyone who fights it does. AZGF and the SO are of the opinion that it's not up to them to determine, in the field, whether a motorcycle is designed primarily for off road use; so they write you a ticket. Is not having to go to court worth the $25?"
So, I bought one.