replies to threads like these are funny...
bfg, evga, xfx all use the same pcb and components.
other than some specialized heatsinks you'll find now and then (in general they all stick with the reference hsf, and the 'special' coolers tend to be more gimmick/marketing than performance oriented).
used to be that xfx tended to o/c their cards more, but evga and bfg (with their new oc2 series) generally match their clockspeeds.
what differentiates them is the color scheme, amount of overclock, price, warranty policies, and the quality of the warrantly & support, and sometimes the bundle (my evga came with a might and magic game and my bfg came with a t-shirt.)
bfg, evga, and xfx all offer 'true' lifetime warranties (xfx has a 'double lifetime' meaning the warranty is applicable to the second owner).
evga specifically states overclocking or changing the heatsink does not void the warranty (as long as all original parts are entact for rma). they also offer a 90-day 'step-up' program the others don't.
overall bfg and evga have a better reputation for service/support than xfx, but you'll find good and bad things said about any of them...
personally i've had very good support/service from bfg. and while i've had their hardware, i have not had personal exp. with either evga or xfx service/support (tho i received my evga rebate in about 3 weeks, which is really fast).