Intel Core i3 4170 's Advantages
Higher base frequency (3.7GHz vs 2.8GHz)
Lower TDP (54W vs 65W)
Intel Core i5 8400 's Advantages
Released 2 years and 7 months late
Higher specification of memory (2666 vs 1600)
Larger memory bandwidth (41.6GB/s vs 25.6GB/s)
Larger L3 cache size (9MB vs 3MB)
More modern manufacturing process (14nm vs 22nm)