So an overclocked 7950 will actually give $100 worth of performance over an overclocked 7850? I'd like to go for the 7950 and be a bit more future proof as long as it isn't a 50% price increase for 20% more performance.
I personally think the HD 7950 is a better card as you will have more graphics punch and the VRAM will really come in handy if you ever decide to game on larger resolution monitors or even when Unreal Engine 4 games come around (I think Unreal 4 even at 1080p will tax 2GB cards pretty good.) For $310, when you OC the 7950, you can have GTX 670 performance for about $90 cheaper.
Hmm. It differs only 1 tier. Ask yourself the question if it is worth 100 dollars for a better card (1 tier higher). Of course like the guys mentioned above the 7950 is better. The more you pay the better. You get the quality for what you pay for but do you really need it? If the answer is yes then go for the 7950 If no spare some bucks and get the other card.