Well Shaft drive gives you more torque and very low maintenance needed but also kinda jerky because its all metal to metal. Whereas belt is very smooth comfortable not as torqueish also you have to replace belts. Now having a vstar i obviously have shaft and will swear by it mostly cause I don't like Harley's very much and they use almost exclusively belt drive.
and before someone says somthing yes i know that Yamaha uses belt on some bikes
Belt drive assemblies are lighter than shaft drive assemblies. So there is a bit of weight savings there which may make a difference in the acceleration of a similar sized bike. Not sure about maintenance on shaft drives but I believe that the belts last quite a long time. I think I read a 30k mile replacement in my manual.
The difference is not earth shaking. Buy the bike you like and you will be happy. I hear numbers for the life of a belt more like 100,000 miles but You need to check it more often and probably replace it around 70,000 to be sure you don't get stranded. I have 40,000 on my belt. The belt gets a little more power to the road because it does not have two sets of right angle gears one at each end. Right angle gears have slightly more loss. This would also mean a small gain in fuel mileage.
The belt is supposed to be smoother, I never noticed any difference. Harley went from a chain to a belt. Yamaha is going from shaft to belt on its last four models. Neither is having problems with belts. I'm sure some failures have happened. A few have gotten a stone in the belt, but a few have had failure of the rear end of the shaft drive also. Given a choice I would take the belt, but if I were looking at a nice shiny touring bike with a shaft I would buy it. The belt seems to be the way things are going but Yamaha and some others have certainly been successful in the past with shaft drives.