I find that 3412 works great against 4231 either variation because it spreads the field out. However, when people play with all of their CAM's on stay forward, it puts my 3 cb's under some duress.
And 433 always kills 3412 because the wingers are usually so far wide it just spreads everything out.
Now on the converse side, 4312 is great against 433 because I have 4 defenders and they got everything situated. But against 4231 it struggles because of how narrow it is and since all garbage 4231 players do is just pile everyone in the box, I'll have no width at all.
So if you had to choose between those two, which one would you use?