The AMD RX 6400 is the objective winner of this comparison, securing a victory in six out of thirteen measured specifications. Its most significant advantage over the competition is a 73% higher boost clock, which provides a substantial lead in raw frequency capabilities. While the AMD RX 580 maintains a notable 300% advantage in memory bus width, the overall spec-win count favors the newer architecture for its superior clock speed performance.

Users prioritizing high-frequency operation should select the AMD RX 6400 to leverage its significant boost clock advantage. Conversely, those who require a wider memory bus for specific data throughput needs should choose the AMD RX 580, as it offers a 300% improvement in that category. Your final decision should depend on whether your specific workload benefits more from the increased clock speed of the newer card or the wider memory bus of the older model.