The BV 500, it's got the power and weight you'll need for such a long time in the saddle. The smaller machines will be operating at the top end of their performance, and you can feel the strain after a while, so go for the comfort that is afforded by power and weight.
Check out things like personal fit of the seat and handlebars, leg room, mirrors, brakes, all the things you'll be using a lot, and go for the most comfortable fit.
Fuel consumption can be managed by driving style, so I don't think that would be an issue of concern, they're all very efficient.
The 300i would be another good choice, it's a little lighter and still has nice power, and unless you're touring forever, it would be well rounded for your riding when you get home.
I have an Xciting 250 and an Xciting 500, and the 250 is more fun around town, but the open road is unquestionably the domain of the mighty, mighty 500 X, especially with a the big Givi windshield. It's got a quiet, easy ride that eats up the miles, and the kilometers don't even register.