Intel Core i3 7100T Advantages
Better graphics card performance
Higher base frequency (3.4GHz vs 2.9GHz)
Lower TDP (35W vs 65W)
Intel Core i5 9400 Advantages
Released 2 years late
Higher specification of memory (DDR4-2666 vs DDR4-2400)
Larger memory bandwidth (41.6GB/s vs 38.4GB/s)
Larger L3 cache size (9MB vs 3MB)