The Intel Core i7-8700K is the objective winner of this comparison, securing more total spec victories than the Intel Core i5-8400. The most significant technical advantage held by the i7-8700K is its thread count, which is 100% better than that of the i5-8400. While the i5-8400 maintains a 49% advantage in MSRP, the i7-8700K provides superior hardware specifications across the majority of the measured categories.

Users who prioritize maximum thread capacity for their computing tasks should select the Intel Core i7-8700K to leverage its primary performance advantage. Conversely, the Intel Core i5-8400 is the appropriate choice for budget-conscious buyers who value the 49% MSRP advantage over the additional threads found in the higher-tier model. Choosing between these two components depends entirely on whether your primary requirement is the increased thread count or the lower MSRP.