HD 7950(1150 mhz) vs GTX 660 Ti(1346 mhz) .
http://www.hardocp.com/article/2013...oc_gtx_760_overclocking_review/5#.UkcU-H_3x8E
15% faster in Crysis 3 High settings 4x SMAA, 10% faster in Farcry 3 Ultra 4X MSAA, 20+% faster in Tombraider
3GB VRAM. better suited for next gen games like BF4. and then comes the added advantage of Mantle in BF4 and other Frostbite 3 titles.
the decision is quite easy. at average overclocks HD 7950(1.15 ghz) is a GTX 670(1.25 ghz) competitor.
PCS+ HD 7950 has one of the quietest coolers. unlocked voltage. at USD 210 (180 after MIR) its a amazing deal.
http://hexus.net/tech/reviews/graphics/35033-powercolor-radeon-hd-7950-pcs/?page=12
http://www.techpowerup.com/reviews/Powercolor/HD_7950_PCS_Plus/26.html
http://www.vortez.net/articles_pages/powercolor_pcs_hd_7950_review,9.html
http://www.guru3d.com/articles_pages/powercolor_radeon_hd_7950_pcs_review,9.html
http://www.newegg.com/Product/Produc...82E16814131458
I don't OC though, and today's perf is extremely close according to those graphs. So really I would only be doing it for the assumption that future games will faster on the 7950 due to Mantle, next gen consoles, and the 3 GB memory. It's a gamble, but it might make sense, not sure.
Also regarding the PowerColor, it's a little concerning that it's been out almost two years and has only 17 reviews on Newegg and two reviews on Amazon.