Intel Core i5 9400 's Advantages
Released 2 years and 8 months late
Integrated graphics card
Higher specification of memory (DDR4-2666 vs DDR4-2133)
Lower TDP (65W vs 140W)
Intel Core i7 6800K 's Advantages
Larger memory bandwidth (76.8GB/s vs 41.6GB/s)
Higher base frequency (3.4GHz vs 2.9GHz)
Larger L3 cache size (15MB vs 9MB)