The AMD Ryzen 5 9600 is the objective winner of this comparison, securing victory across nine of the fourteen evaluated specifications. Its most significant technical advantage is the L2 cache, which is 300% larger than that found in the Intel Core i5-8400. This substantial increase in cache capacity provides the primary performance edge for the newer processor, allowing it to outperform the older model in the majority of measured categories.

Users prioritizing modern architecture and superior cache capacity should select the AMD Ryzen 5 9600 for their build. Conversely, the Intel Core i5-8400 remains a viable option for those specifically seeking a lower Max Turbo Power, as it holds a 26% advantage in that metric. Choosing between these two components depends on whether your requirements favor the expanded cache capabilities of the newer processor or the specific power profile of the older model.