I have a little bit of everything. Harley, Vespas, Scooters, Mopeds, and my trusty little motorized bicycle. While I will say, the Moped (when stock) is a lot more reliable then your china girl 2 stroke motorized bike), I find myself riding the Vespa a lot more. It's a lot more fun, and people love to see you on it.
However, I have a LOT of enjoyment riding my motorized bicycle that I built myself. It's a 7 speed (jackshaft) and it can handle anything. So, it's kinda what you want to do. my moped is VERY worked. It has a 70cc top end, bigger carb, expansion chamber exhaust. But, I know that it can break down at any minute due to all the work that's done to it. A motorized bike is the same way. But, if you keep a moped stock, they'll run forever...