NVIDIA GeForce GTX 680M 's Advantages
More VRAM (4GB vs 2GB)
Larger VRAM bandwidth (115.2GB/s vs 32.00GB/s)
960 additional rendering cores
AMD Radeon R5 M255 's Advantages
Released 2 years and 4 months late
Boost Clock has increased by 24% (940MHz vs 758MHz)