Comparison of Sapphire Radeon RX 6900 XT video card vs Gainward GeForce RTX 2080 Phantom GS video card by specifications and benchmarks. Sapphire Radeon RX 6900 XT runs at 1.825 GHz base clock speed and has 16 GB of GDDR6 memory, while video card Gainward GeForce RTX 2080 Phantom GS runs at 1.515 GHz base clock speed and has 8 GB of GDDR6 memory. The TDP of the first video card is 300 W, and the second is 215 W. Compare the table of benchmark results to find out which graphic card is better.