Last April I was facing the same choice....what adventure bike to buy. Been a loyal Honda guy for most all of my motorcycle purchaces, but Honda does not offer anything stateside in this category so I entered the search w/o brand loyalty.
First rode the Yamaha. Felt good. Thought that was the one.
Next rode the KTM 990 (regular). Liked it better than the Yamaha because it felt like I was sitting aboard my 450X but better suited for the road.
Lastly, I rode the 800XC. Although very fast (in upper revs) and cool looking, it did nothing for me and I turned around after only 10 minutes knowing this bike wasn't what I was looking for after riding the KTM. Primarily, no tourqe and limited wind protection sealed it's fate compared to the KTM.
The KTM felt like a big-boys toy compared to the buzzy Triumph.