So I spent all of my money (I had like 15m left over lmao) on a cap4 cruiser to do missions. I took this approach as a normal player, not a tryhard. I took whatever highest missions were offered without resetting the board, I did them at a major base in house space, and I did them back to back (I'm subtracting an hour for setup/an RP encounter I had). Most of my missions were against gunboats, but I had 3 against high level fighters and 2 against cruisers (both failed, but one mission I killed a cruiser before dying)
In 2 hours (3 before the subtractions) I made 95 million credits. A real far cry from what I'd get from ore trading. If I minmaxed I'm sure I could have squeezed out some more, but I think it's best to approach this comparison under the 'typical player' idea.