Please provide a replay of both a DSHK and an MG42 attacking light vehicles. Make it in a custom match so both weapons attack the same vehicle and make them attack the vehiles of both armies.
I tested it, AP on the DShK has little or no effect. Surprisingly, API on the MG 42 hitting the rear end of a T-34/76 can take out nearly half it's health if it sits there for the entire duration. Both are roughly equally effective against scout cars without any abilities, which is not very much, but if it sits there for 20 seconds it's dead.
No replay because I used my personal test map and you wouldn't be able to play it without said map.