DT,
I did extensive testing, offline, during the Italy SEOW on how best to crack the two Royal Navy Battleships. As I mentioned in an earlier post, I used the He-111 H6 throughout. As it can carry two torps or a pair of SC 2000Kgs or a pair of PC 1600s.
I must of attacked the Prince of Wales Battleship no less than 30 times, and I can't remember the exact figures, but I do know the torps performed the worst. With unlimited ammo setup, it would take several drops of pairs to sink it. I'm guessing something around 6 torps at least.
Whereas the SC 2000s were the best overall. I can't remember if just a pair could do it, I think it might need at least 1 more 2000Kg bomb. And the PC 1600s needed a bit more again I believe.
After about 3 unsuccessful attacks with He-111s in the Italy SEOW, I tested offline again with the Bf-110, with a pair of SC 500s, as Kling mentioned above. And 3x Bf-110s armed this way will sink a PoW BB, as witnessed.
The only good thing about torps I believe, is their ability to allow you to shoot at stationary ships from miles away.
And as Kling again mentioned, with BBs, the armoured belt would probably of hindered the torps power. Whereas skip bombing with SC500s or SC2000s might of led them to skip over the belt and hit the ship above the sealine.