I have owned a variety of big adventure bikes - ktm 950s, ktm 1190, bmw 1150gsa, 1200gs all were great road bikes but for me on singletrack they are all too big, too heavy, too much plastic to damage, too valuable, but they were all fine for gravel roads and they did look super cool parked outside Starbucks.
Medium size bikes I’ve owned Honda xr650r, xr400, couple of ktms 450exc’s all have been good on singletrack but not good for long road rides.
I think Adventure bike style has paid off well for the manufacturers, to me bikes in that category are great road bikes, with comfortable ergonomics. Now that the trend for choppers and supersports bikes has largely passed I think the manufacturers are doing a great job of promoting the adventure bike and lifestyle.
I bought a wr250r earlier this year to run sections of the TAT, while I had doubts about riding a small bike on long road sections the huge amount of positive long distance ride reports and reviews on
www.advrider.com convinced me it was worth trying. With a small screen, soft panniers and a few mods it is a fantastic ‘adventure’ bike that is if you want to ride singletrack after riding hundreds of miles on road. More power would be nice on the road, but the saying that it is more fun to ride a slow bike fast, than a fast bike slow is so true.
Luckily there are lots of great bikes out there, it all depends on what you want to do with it.