I have owned both. A 2001 KLR250 and a 2007 XT225. And a friend of mine got good deals on one each of these used, and decided he would keep the one he liked best. He went with the KLR250 as the keeper, but he is tall. For a taller rider the KLR250. But, don't sell the XT225 short. It has excellent power and the 6 speed trans is nice. I'm 5'10" or so, and the XT225 was fine for me. And I actually got over 100 miles per US gallon when just thumping around at 45 mph and under. Easy to work on, including valve adjustments. The KLR also has screw type valve adjusters, but, being water cooled, you have more crap to remove and reinstall for access to the valve adjusters.
I loved both of those bikes. If I could find a clean used KLR250 here on the Big Island of Hawaii, or one in the San Diego area (for lowest shipping cost), from a dealer, I wouldn't hesitate to get another one.
And the KLX250 is a great bike too from what I hear. I think they may sit a bit taller than the KLR250.
Jon in Keaau, Hi. USA
2008 SYM HD200 (wife's ride)
2009 Kymco People 150 and coming soon, another dual sport mc