Graphics cards and black friday/cyber monday

I've been containing myself from buying many components for a new build until this week in case of any sales.  I've been eyeing the HIS Radeon 7870 which is now on sale on newegg for $189.99.  However, through craigslist I have found someone willing to sell me a new GTX 670 (this one actually http://www.newegg.com/Product/Product.aspx?Item=N82E16814130782&nm_mc=AFC-C8Junction&cm_mmc=AFC-C8Junction-_-na-_-na-_-na&AID=10446076&PID=3938566&SID=) for $200.  I know it retails for much higher but i don't really know why.  I'm feeling that I'm going for the craigslist deal but I was wondering if anyone could tell me the big differences in these cards.