Intel Core i5 7400 's Advantages
Better graphics card performance
Lower TDP (65W vs 95W)
Intel Core i7 8700K 's Advantages
Released 9 months late
Higher specification of memory (2666 vs 2400)
Larger memory bandwidth (41.6GB/s vs 35.76GB/s)
Higher base frequency (3.7GHz vs 3.0GHz)
Larger L3 cache size (12MB vs 6MB)