Windforce>phantom
simply because Gigabyte CS>Gainward CS
Also, judging by reviews, the windforce cards and phantoms are both very similar performers. Phantom 2.5 slots are quieter, otherwise, both dual slot cards are similar
Not having used any CS from either company I can't comment, but the gigabyte 670 is probably the better performing card of the two. A lot of people in here having been getting good overclocks with the windfugly (can't resist) I cannot deny that. However, this is the first attempt at overclocking a phantom, and it's only one sample I've seen in this forum. One swallow doesn't make it summer (but it does make a damn good date ).