Turn  

Symmetrical shape. Black gets ahead. But yes, it's an occasionally Possible compromise for White.

Better  

Simply playing for the top first is more reasonable. W is left with better aji, even though B has some possibilities too.

Thanks for the answers. Given the configuration (Black had a wall facing the top in the topleft corner) I guess I should have considered the large knight approach. Actually I expected Black to play knight's jumps on both sides... But it didn't turn out that way !