You are in for a lot of answers... here is my opinion...
Your owner's manual does a great job of explaining oil viscosities for your riding conditions. I live in Ottawa Canada, and have broad temperature ranges to cope with as well. Personally I favour the wider range of synthetic oils, something in the 15W50 category. The LT is water cooled and as bit easier on it's oil as it manages temperature with cooling fans and water jackets. My other bike is an air cooled Yamaha V Star 1100 and synthetic oil gives it some temperature headroom for rush hour traffic in August.
I also use synthetic in all my air cooled engines and truck, they are susceptable to high temperatures in the engine block due to limited cooling or up hill towing.
The important thing is buy properly rated oils by spec, and stay in your temp range, if you are in the Alps all the time, might want to add a few degrees headroom or long climbs. Synthetic will cost more, but if you do your own oil changes, it should balance out.