Here in Greece were motorcycle delivery is extremely widespread (in a 2km radius, there are around 80-100 coffee and food shops delivering to my place), the weapon of choice for delivery guys are either underbones (semi-automatic bikes like the Supercub) or low displacement scooters, like the PCX-125.
While underbones used to be fuel-efficiency kings, recent scooters have managed to get to their level, while offering a better working experience (no gears to change, ABS is more prevalent, better handling and rigidity, esp with a box mounted). The start-stop equipped scooters in addition have more reliable starters and the batteries can withstand the numerous short trips better. Also, having your feet sit on a platform protected from waterspray is nice.