I've never ridden a Stelvio, but they certainly are an intriguing looking bike. I suspect they are more "characterful" than the Yamaha, with all the baggage that this entails.
I did ride a 2014 Super Tenere ES and was a bit underwhelmed. I really expected it to be a quantum leap better than my tired old Suzuki ManStrom DL1000, and frankly, it just wasn't better enough. (The 2014 FJR ES that I rode the same day was a quantum increment over my old 2005 FJR, and so I bought that on that day)
Sure the Tenere has a shaft drive, but that is just not the "end all and be all" for me that it is for many others. Certainly not on a bike that will see dirt road duty, as changing gearing is a PITA on any shaftie. I tossed a 1 tooth smaller front and 3 tooth larger rear onto the 'Strom and it completely transformed its off pavement manners, and actually helped on pave' also. I guess if they really "got it right" with the stock gearing it would be a non-issue, but often they will have missed the mark at least a little bit.
Also, the S10 is bit heavier than my old Strom and it felt like it during the test ride (I was led to believe it carries its weight lower). I think if I am ever going to replace the Strom it will end up being with a lighter bike with better suspension like a twin KTM or similar. Unfortunately Suzuki missed the opportunity to make a big change to the Strom with the latest Gen 2 revision. It looks better, but it's the same basic bike underneath and has some of the same foibles, so I would not recommend one of those.