The Intel Core i5-12400 wins in 9 out of 14 comparable specs, with 2 ties. Its biggest advantage is L2 Cache (400% better).
Core i5-9600K wins in 3 specs (Base Clock: 48% better).
Recommendation
Choose Core i5-12400 if you want the best overall performance — especially l2 cache.
Choose Core i5-9600K if base clock matters more to you.
