The Intel Core i5-12400 is the objective winner of this comparison, securing victory across eight of the fourteen evaluated specifications. Its most significant technical advantage is the L2 cache, which is 400% larger than that found in the alternative. While the Intel Core i5-9400F maintains a lead in power efficiency with a 44% lower Max Turbo Power rating, the superior cache capacity of the newer model provides a clear architectural edge in overall component capability.

Users prioritizing modern architecture and increased cache capacity should select the Intel Core i5-12400 for their build. Conversely, the Intel Core i5-9400F remains the appropriate choice for those who specifically require a lower Max Turbo Power profile. By focusing on these distinct advantages, buyers can align their hardware selection with either the performance-oriented cache improvements of the newer processor or the power-constrained operation of the older model.