Motor oils have 2 components: The base oil.. these are Group I and II (mineral), Group III (hydrocracked mineral which they also call as "synthetic"), Group IV (PAO - the true synthetic) and Group V (other synthetic) ... the other component are the oil additives they mix with these base oils like detergents, friction modifiers, viscosity modifiers, anti-wear additives, anti-foam agents, seal conditioners, to name some. One of the main characteristic of synthetic based oil is it has a longer life than mineral oil... for me, it doesnt matter because I still need to change oil regularly because of the dirt suspended in there. Diesel oils (Rotella, Delo, Rimula) are good because they have higher detergent content compared to other oils... I use a Scooter specific oil because it has friction modifier additives and is a low friction oil. I'm more concerned about the additives in the oil rather than the base oil...
However, these scooter specific oils with the JASO MB rating are not compatible with other scooters that uses a multi-plate clutch (like the Piaggo BV350) instead of the usual centrifugal type clutch... Using an oil with friction modifiers will make multi-plate clutches slip...