Comparison of ASRock Radeon RX 6600 Challenger ITX video card vs ASRock Radeon RX 6900 XT Phantom Gaming D 16G OC video card by specifications and benchmarks. ASRock Radeon RX 6600 Challenger ITX runs at 1.626 GHz base clock speed and has 8 GB of GDDR6 memory, while video card ASRock Radeon RX 6900 XT Phantom Gaming D 16G OC runs at 1.925 GHz+ 5 % base clock speed and has 16 GB of GDDR6 memory. The TDP of the first video card is 132 W, and the second is 300 W. Compare the table of benchmark results to find out which graphic card is better.