Odd choice of bikes - but one I keep seeing. I owned a 2003 Burgman 650, a 2005 Burgman 400 (the wifes), and a 2006 Vstrom 1000. Now I have a 2009 XCiting 500... Perhaps you should consider an XCiting 500?
The XCiting 500 will cost you less than the Burgman 400 but have twin front discs instead of a single, have more power - but less storage. The Burgman 400 sits different than the XCiting's too - your knees will be higher. The Burgman has a lower seat - and the passenger sits higher - so 2 up riding isn't as stable. The mpg figures are comparable.
The VStrom's are excellent bikes and will handle tons better than an XCiting could imagine. The 1000 is a great bike for 2 up or riding long distances at a good pace. What it doesn't do well (why I traded down) is ride smoothly at slow speeds. Both VStrom's are tall and a bit on the heavy side - but their height/weight disappear at speed and they are very comfortable. The 650 could use more power for passing while going uphill and riding tandem (not a big deal) where the 1000 has plenty of grunt for anything. But the 1000 needs a gear below 1st for offroad, and it isn't smooth at neighborhood speeds. I loved my 1000, but after becoming a single parent I wanted to be able to carry my daughter on something larger than my Zuma 125 - and the VStrom was just too cumbersome at the speeds I wanted to carry her.
I cruise at 80mph on the XCiting 500 with no problem. It's only problem is the same as your XCitng 250 - the suspension is meant to be comfortable instead of for handling. You can only get so good of handling when the engine moves up and down with the rear wheel anyway so oh well...
