ATI Radeon HD 5770 Mac Edition 's Advantages
Larger VRAM bandwidth (76.48GB/s vs 73.60GB/s)
288 additional rendering cores
AMD Radeon R9 255 OEM 's Advantages
Released 3 years and 5 months late
Boost Clock930MHz
More VRAM (2GB vs 1GB)
Lower TDP (65W vs 108W)