The major advance in the US TDCs was incorporation of a real-time target tracking system linked to the angle solver. It took data from a number of inputs, including the sonar and radar, and allowed the attack officer to predict where the target would be. Made shooting solutions a lot more accurate. If you took a couple of bearing/range readings at, say, five minute intervals and fed the data into the TDC, you could take a final reading five minutes later and the target is at the exact bearing and range on the TDC, your chances of hitting it are a lot better than they would be if you had to work out a new solution with each observation and estimate where the target was going to be by the time you fired.

For an electro-mechanical unit, they were good enough that a gentleman of my acquaintance said he couldn't get a PC to do the same calculations accurately until the first Pentiums came out. (When the Iowas were reactivated a few years ago they also kept the electro-mechanical targeting systems, since they were as or more accurate than anything electronic, and a lot more survivable.)

J.T. McDaniel