I wouldn't unless it was absolutely huge % wise, not just actually money wise.
Although the cards run the same for the most part (not these 2 though, since the EVGA is overclocked) the company warranties are a big thing.
Evga Lifetime + 90 day step up.
BFG LIfetime + 100 day Step up.
XFX DoubleLifetime + more freedom with Card tweaking (cooler change etc).
Yup, i agree with your opinion.
But i don't like "superclocked" thing, because i can buy the normal card and then OC it by myself...
But again, that's just me.