ATI Mobility Radeon HD 5850 Mac Edition 's Advantages
Larger VRAM bandwidth (64.00GB/s vs 28.80GB/s)
656 additional rendering cores
Lower TDP (30W vs 35W)
NVIDIA GeForce GT 555M 's Advantages
Released 2 years and 2 months late
More VRAM (2GB vs 1024GB)