Actually it doesn't in Techpowerup, Because techpowerup used more games to test on:
But in fact that the 7970 is just %1 percent faster but cost ~$60 more, there is absolutely NO point of getting the 7970 over the 670. Unless your friend are not a gamer and you want to do compute stuff. Which is a different case (the 7970 will be a much better choice really). Tell your friend don't be that much of a fanboy
tell him/her performance and price matter most OK!