The AMD Ryzen 9 3900X is the objective winner of this comparison, securing victory in seven of the fourteen evaluated fields. Its most significant technical advantage is its L3 cache, which is 256% larger than that of the Intel Core i5-12400F. This substantial memory capacity provides the primary performance edge for the AMD Ryzen 9 3900X, positioning it as the superior option when prioritizing raw hardware specifications over the alternative.

Users who require the expanded L3 cache capacity should choose the AMD Ryzen 9 3900X for their system builds. Conversely, the Intel Core i5-12400F is the better selection for budget-conscious buyers, as it holds a 65% advantage in MSRP. Selecting between these two processors depends entirely on whether your priority is the superior cache architecture offered by the former or the significant cost efficiency provided by the latter.