From Fangraphs:
"xFIP has one of the highest correlations with future ERA of all the pitching metrics. Only SIERA out-paces it."
Here are some links to studies, if you're so inclined to read them:
http://www.fangraphs.com/blogs/are-pitching-projections-better-than-era-estimators/
http://www.hardballtimes.com/should-we-be-using-era-estimators/
I do agree with you that Price's high K rate makes his season look better than Wright's in terms of WAR. IMO, Price's stats are fluky this year because he is one of the best in terms Ks, but the worst in terms of hits allowed. There are always going to be exceptions when it comes to stats. But in general, K/B ratio, and therefore stats like SIERA and xFIP, do a pretty good job at how good a pitcher is performing.
That is not to discount ERA-, WHIP, and OPSa in any way, as I like those stats too.