I had a 250 GTS for ten months and 10,000 miles from new. It developed endless issues with electrical relays and fuel pump issues and i got rid of it. It was simply too unreliable.
It was without doubt the most comfortable motorcycle i have ridden. It is fast smooth and highly addictive. However an 85mph 250 single with lots of bodywork that returns 65mpg easily, requires enormous technological wizardry which is expensive to build and appalling to maintain. The rear wheel is impossible to remove and the tire lasts but 3500miles, the exhaust has a split to remove the muffler whose bearing is a notorious source of problems. But you can easily ride it on gravel.
With so little riding done I suggest the GS is too much motorcycle for you. When a thing gets overhwleming in size and weight the joy of being able to slip out for a quick ride or for grocery run disappears. The Vespa, all $7400 of it might achieve a higher frequency of use. My tales of woe are rare and with the sort of low mileage you seem likely to achieve even with a lot more use, tire wear, belt wear (change every 10,000 miles these days Vespa says) and exhaust bearing woes will be of little consequence.
If you plan on doing a lot more miles I'd say look elsewhere but a huge BMW not being ridden doesn't do you much good while a pleasant cruise on the nimble GTS might be just the ticket. When running it is a great ride and it looks a million bucks.
My Bonneville by comparison has 72,000 miles in five years and is going strong. I don't see a GTS accomplishing that. But that isn't your concern (or mine anymore!).