We choose DR650s for our trip, good bike one up and although we had serious engine issues the rest was good (my DR650 at home has been bomb proof)
When we took to riding two up we choose the 950 SE with 30L big tank plus CJ aux tank 8.2 L, the longer wheelbase of the 950 SE at 1577 over the DR 650 at 1490 means better stability on gravel and better room for two of us.
My next trip which will be solo will be a DRZ400, Colbatch bags and the usual 28 L safari tank and, bashplate etc, but that is a boys trip.
You have to look at what you want from a bike for "adventure", some like adventure touring/travelling, some like adventure riding and there is quite a difference.
When two up with house and contents our bike is a tourer/traveller, arrive at destination, ditch both cases and top box and I have an adv ride bike albeit not for super tight stuff for too long or the fun factor goes out the window.
This is how she sits as a traveller
This is how we go exploring and an adventure rider sans luggage (and riding gear
) when we got lost and had to ride up a creek bed for 1 km.