The RX 7800 XT 16GB has about 24% more memory bandwidth (624 vs 504 GB/s). Batch-1 decode tracks bandwidth closely, so a model that fits both cards should decode roughly 24% faster on the RX 7800 XT 16GB. The RX 7800 XT 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 RX 7800 XT 16GB but not the RTX 4070 12GB: gpt-oss-20b (21.5B). MSRP is $599 for the RTX 4070 12GB vs $499 for the RX 7800 XT 16GB. 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 RX 7800 XT 16GB posts the higher tok/s in 32 rows vs 8. Methodology.