The Arc A770 16GB has about 23% more memory bandwidth (560 vs 456 GB/s). Batch-1 decode tracks bandwidth closely, so a model that fits both cards should decode roughly 23% faster on the Arc A770 16GB. The Arc A770 16GB fits more of the catalog at Q4/8K — 25 vs 18 of 61 models (16 vs 12 GB VRAM). Largest model that fits the Arc A770 16GB but not the Arc B580 12GB: gpt-oss-20b (21.5B). MSRP is $349 for the Arc A770 16GB vs $249 for the Arc B580 12GB. MSRP is a launch list price, not live retail — Amazon prices move; click through for the current price. In the Q4/8K head-to-head below (40 shared models), the Arc A770 16GB posts the higher tok/s in 33 rows vs 7. Methodology.