One thing you need to do, whatever you buy, is to make sure you fit on it. If possible, test ride it. I'm 6-2. The seating position of the PCX sucks for me. My knees hit the handlebars on the Zuma when turned but they may be adjustable. I fit pretty well on my 09 Super 8 and my Aprilia Sport City 250. I occasionally ride both of them off road.
Another scooter you may want to consider if you can find one is the Sym HD200. The larger 16" wheels might do better in the dirt. The motor, although only 171cc is a real powerhouse capable of running 70+
Keep in mind that scooters tend to have limited suspension travel. While they can be ridden off the pavement, you'll have to go much slower than you would on a dual sport motorcycle.