actually, it stacks less and less.
only real gain is increase in crit chance.
adv gives you +3,33 on average
E.Accuracy gives you +1,66 on to of advantage. So half extra of normal advantage bonus
4d20D3 would give you +1 over 3D20D2, and
5d20D4 would give you +0,66 over 4D20D3
crit chance is...