From the best knowledge we have from our best engines, A is the better move (though I don't think we have formally proven such yet).
But if you play A, you are playing your opponent in a game of memorization.
If you play B, your opponent loses any memorization advantage. Thus they must play based on ability other than memorizing responses.
For a player whose memorization ability is equal or worse than their ability to play based on other ability, choosing move B is clearly the worse option. But if the player is one whose memorization is better than their other abilities at chess, then playing B means fighting them in an area they are worse at. The advantage of this can easily outweigh the disadvantage of move B compared to A in general.
Imagine a military commander choosing an engagement over terrain more familiar to their side even though it is a worse engagement if both sides had equal knowledge of the terrain, because the terrain knowledge more than compensates for the negatives.
Move A.
Move B.
From the best knowledge we have from our best engines, A is the better move (though I don't think we have formally proven such yet).
But if you play A, you are playing your opponent in a game of memorization.
If you play B, your opponent loses any memorization advantage. Thus they must play based on ability other than memorizing responses.
For a player whose memorization ability is equal or worse than their ability to play based on other ability, choosing move B is clearly the worse option. But if the player is one whose memorization is better than their other abilities at chess, then playing B means fighting them in an area they are worse at. The advantage of this can easily outweigh the disadvantage of move B compared to A in general.
Imagine a military commander choosing an engagement over terrain more familiar to their side even though it is a worse engagement if both sides had equal knowledge of the terrain, because the terrain knowledge more than compensates for the negatives.