The Intel Core i9-14900KS wins in 9 out of 14 comparable specs, with 1 tie. Its biggest advantage is L2 Cache (2033% better).
Core i5-8600K wins in 4 specs (MSRP: 63% better).
Recommendation
Choose Core i9-14900KS if you want the best overall performance — especially l2 cache.
Choose Core i5-8600K if msrp matters more to you.
