AMD Ryzen 9 7940HS 's Advantages
Higher specification of memory (LPDDR5x-7500 vs DDR5-5600)
Higher base frequency (4.0GHz vs 3.8GHz)
Lower TDP (35W vs 35W)
AMD Ryzen 7 7840H 's Advantages
Better graphics card performance
Newer PCIe version (4 vs 4.0)