Here's a rough breakdown (in my opinion of dualsport bikes):
800-1200cc: big bikes, fairly heavy when off road. They are comfortable and have good acceleration/handling on the road. Great for multi day trips and adding panniers. Off road they can be a handful and heavy to pick up
when you crash.
600-800cc: better off road, and they weigh a lot less. still not as small as a dirtbike to pickup
when you crash, but better than the big bikes. You lose some power on the road, noticibly at higher speeds. These bikes are usually single cylinders and can vibrate at interstate speeds. Usually not as comfy as a big bike and not as off road capable as a dirtbike, but a solid blend.
under 600- more of a dirtbike style. best in the dirt and least best on the street (with exceptions) Awesome for around town with sumo tires. Very light weight and vary capable in the dirt. But it would not be fun to ride one of these to Alaska.
The BMW/Triumph 800 are both great bikes. Personally I'm partial to the KTM 950/990 Advventure. BMW1150/1500 and the Yamaha Super Tenere are a little more road worthy than offroad. The most important advise I can give, is try all of the bikes first. Sit on the ones you are interested and take them out for a spin. For example, the F800 and KTM990 are both great bikes, but
VERY different.
Go to
www.advrider.com and read for the next fifteen days.