Comparison of ASRock Radeon RX 6600 XT Challenger D 8GB OC video card vs XFX Speedster MERC 319 Radeon RX 6900 XT Black Gaming video card by specifications and benchmarks. ASRock Radeon RX 6600 XT Challenger D 8GB OC runs at 2.000 GHz+ 2 % base clock speed and has 8 GB of GDDR6 memory, while video card XFX Speedster MERC 319 Radeon RX 6900 XT Black Gaming runs at 1.950 GHz+ 7 % base clock speed and has 16 GB of GDDR6 memory. The TDP of the first video card is 160 W, and the second is 300 W. Compare the table of benchmark results to find out which graphic card is better.