What is the correct cube action for both players in these two similar positions?

The double should be obvious in both positions but A is a take and B is a pass even though black has a lower pip count in position B.

It is a question of timing. In both cases, if black rolls a 5 or 6 it will be running a checker from the back. But what if black were to get a string of smaller numbers. In position A there is the timing to move checkers into the board and fill the gaps. In position B the two checkers on the 21-point have been moved to the 24-point already so black has less chance to keep it's board and without that timing it cannot contain a checker when black gets a hit.

There is a second reason also. If black does manage to hit a checker in position A, it might well enter on the 24-point and get stuck there whereas in position B, the 1-point is blocked meaning that when white enters it has a much easier route to escape.

It's a small and subtle difference but makes a difference to the cube decision.