Arc B580 12GB vs MacBook Pro M3 Max 128GB for Local LLMs
The Arc B580 12GB has about 14% more memory bandwidth (456 vs 400 GB/s). Batch-1 decode tracks bandwidth closely, so a model that fits both cards should decode roughly 14% faster on the Arc B580 12GB. The MacBook Pro M3 Max 128GB fits more of the catalog at Q4/8K — 47 vs 18 of 61 models (128 vs 12 GB VRAM). Largest model that fits the MacBook Pro M3 Max 128GB but not the Arc B580 12GB: DeepSeek-V4-Flash (158.1B). MSRP is $249 for the Arc B580 12GB vs $4,199 for the MacBook Pro M3 Max 128GB. 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 B580 12GB posts the higher tok/s in 32 rows vs 8. Methodology.