true but when both are oced the HD 7970 will beat the HD 7950 by a good margin
That's incorrect. With both cards overclocked, a good 7950 and a good 7970 will be roughly on-par. Either one could take the lead, depending on how good of a unit it is. This is because the 7970's advantage is almost purely in its clock frequencies (256 cores and related hardware advantage is almost meaningless when there are already so many because scaling with core count increases and such drops as you increase the amounts) and overclocking fixes that. The 7970 doesn't even have more frequency headroom to stop the 7950 from meeting it.