I've owned 5 XT225s as well as a 2012 XT250. Both models are good bikes. What fits best depends on the type of riding you do. For me the 225s are a better fit, lighter than the 250, more nimble and easier to handle off road, plus their 6 speed gear box served me better than the 5 speeds the 250 had.

Others who do more local commuting and highway riding like the 250s better, especially those from 2013 on with fuel injection.

That XT225s have increased in value these past few years seems more a function of their dwindling supply and the strong demand there still is for these classic old school machines.

Bottom line is the bike that's best suited for you is the one that most efficiently serves your needs. If you ride mostly off road, single track, forest service trails and such, the XT225 is likely your better choice if you can find a good one at a decent price. Otherwise a fuel injected XT250 may be just the bike you're looking for.

Either way you have legendary Yamaha reliability and superior design going for you, so saddle up and enjoy!