Have you ridden both?
I struggle with short test rides. A rider just can't get a real feel for a bike in only a few short miles. But after owning my 990 R for about 5 months now I know for me it was the right choice. I think cost and the type of riding a person is buying the bike for, is the reason some would choose the 990 over the Triumph and some wouldn't.
I'm not knockin' the 800 XC,, it's a great bike. A very refined triple cylinder motor, likely, one of the smoothest motors built. Several friends of mine own one and they all seem very happy with the bike. In fact one of my friends whom I respect very much didn't like the 990 due to the fact that it didn't have enough gauges on the dash cluster. I mean,, come on no "Fuel" gauge on a $14,000 ADV bike?
I prefer some of my motorcycles to be just a tad bit truculent.