AMD Radeon HD 7970 GHz Edition 's Advantages
Boost Clock has increased by 13% (1050MHz vs 930MHz)
More VRAM (3GB vs 2GB)
Larger VRAM bandwidth (288.0GB/s vs 73.60GB/s)
1536 additional rendering cores
AMD Radeon R9 255 OEM 's Advantages
Released 1 years and 6 months late
Lower TDP (65W vs 300W)