I'd say tires wear similar on scooters and bikes. Maybe a little less since there is not as much torque chewing up rubber in the rear. I have a silverwing and the OEM Bridgestone Hoop on the rear lasted ~10k miles. The tires tend to be cheaper than larger MC tires too. Most can be had for 50-75 per.
Most big scoots have ~50 liters of storage underneath which is similar to a set of saddlebags or a top box. This leaves room to add both so it is easy to up 150 liters or more of storage on a scoot and still have room for a passenger.
I've never ridden a Burgman 650 so I can't comment on it specifically but I love my Silver Wing and I can't see the need for any other bike. It fills every role imaginable. Auto trans for effortless commuting, low CoG for unloaded fun in the twisties, plenty of power and room for loaded touring.
Scooters are a great jack of all trades. Sure, if I had the money, I would have 2 or 3 different bikes for different occasions, but being limited as I am, I can't imagine having anything but my Silver Wing. It is my car and it does a damn fine job in any situation I put it in.