As the achievement says. It has to be one of the original Heists (not Doomsday or Casino) and can't be Fleeca Job as that's only 2 people. That leaves Prison Break, Humane Labs, Series A, or Pacific Standard.
If my calculations are correct, you're going to want to do it on Prison Break. Assuming that you take 55% of the cut (default) on all Heists except the one where you take 25%, and assuming you're playing on Normal (the total cut is different depending on difficulty) then the total amount you will get from all five Heists is:
25% on Prison Break, 55% on all others: $1,038,300
25% on Humane Labs, 55% on all others: $996,300
25% on Series A, 55% on all others: $1,037,100
25% on Pacific Standard, 55% on all others: $858,300
I'll put the maths in the comments so that a) you can work out the totals for Easy and Hard and b) you can check I haven't messed it up.
Hope this helps!