Zogis? That's a new one for me. There are not many reviews on the web of their products. On their website, the GTX 570 looks like it is the reference model, so there is likely no difference between the two cards. On the other hand, EVGA is one of the most popular and trusted brands with good warranties and customer support... and in this case it's cheaper too. Get the EVGA.
i bought the evga, no one knows the zogis...i have an i7 920 on a asus p6t-se, and 6gigs of ram (patriot viper 1600mhz) , the 570 will "fit" on this configuration or there are a bottleneck in my system (int.)