The bigger fish is winning.
There's always a bigger fish
was going to say that but im glad i didnt... that wouldda been awkward.
Probably neither. Modern submarine on submarine combat is very rare, as the best option is just to call in destroyer support, and back in the day of the Pacific Theater, it wasn't even an option since you needed to surface to see your target, calculate the range and speed of their movement, get your trajectory so that your torpedo would intercept at the right spot, and then sit still and wait for impact or miss to confirm your shot or adjust your aim. /killjoy
Someone needs a sense of humour.