Originally Posted by James Adams
For me, it's about ergonomics. The upright position of most of the adventure-touring bikes is really comfortable.
However, my sport-touring bike gets most of the miles.
+1. I'm surprised so many are going on about suspension travel (which can be compensated for at least in part with adjustment/rebuilding/etc.) when something as basic as ergos can get overlooked. (of course ergos can be adjusted as well!)
If you go to cycle-ergo.com (or sit on a bike, if you have access) you'll notice sport touring bikes (F800ST, VFR, Ninja 1000 and the like) have more forward lean which puts your weight on your wrists at low speed/no acceleration. However, as you get up to speed, the acceleration force plus wind force takes the weight off your wrists. So for a given amount of forward lean, there is a given speed/acceleration combo that holds you up perfectly, without the need to put any weight off your wrists (while taking some tiny bit of weight off your bum too!).
IMO it's easier to be on an upright bike and lean forward when the wind/acceleration picks up, as opposed to trying to lean back on a bike that has the bars far forward and low. But that's just my opinion.
ADV bikes are also generally taller and have less intense knee and hip bends. Whether you like this or not is down to preference - it's all good in my book
If I were describing the two bikes to someone who had never seen either, I'd say ADV bikes were descended (LONG descended) from the big dirtbikes that raced in Dakar and stuff while sport tourers were descended from sportbikes. Both are distance oriented and both are well loved by a lot of people. It's just two directions from which to approach the same problem.