If the IJN had caught the Pac Fleet at sea, I believe that the Pac Fleet would have lost and had been forced to retreat. The IJN had too many technical advantages and there would not have been a one and done attack but multiple attacks. As at Pearl Harbor, the IJN would have attacked the Pac Fleet carriers first. With an advantage of 6 to 3, the IJN would have probably sunk the 3 American carriers or had forced them to withdraw at which time the surface forces would have been unprotected.In December of '41, the Pac Fleet Battleline had very little AA capability. After the 1930's reconstructions, any one of the Pac Fleet Battleships could not count on more than 10-15 5in. and 3 in. combined in upper deck mounts which afforded reasonable arcs of fire. The ammo was not proximity fuse but manually fused and the ships were slow. it would have been a slow retreat under concentrated air attack. I would have to bet on the IJN.