The AMD Ryzen 9 3900X wins in 9 out of 14 comparable specs, with 1 tie. Its biggest advantage is L3 Cache (433% better).
Core i7-8700K wins in 4 specs (Max Turbo Power: 33% better).
Recommendation
Choose Ryzen 9 3900X if you want the best overall performance — especially l3 cache.
Choose Core i7-8700K if max turbo power matters more to you.
