Diesels are quiet but they have so many major drawbacks, size, speed, range, having to surface for snorkels, etc. I'd put any three or four of the Chinese best Kilos or other diesel electric subs against the Seawolf any day, and I'd bet all my money on the only Chinese subs that left that battle were the ones that the Seawolf chose not to send to the bottom. I wouldn't give those diesels a real shot at getting close enough to our Carriers either. The Nimitz's classified speeds match or exceed many torpedos, and that's no small matter. It is a real threat that has to be taken serious, but I don't believe in the final analysis they would have any major victories.
Again, we cannot underestimate them there either. They know of their disadvantages...and they are not going to play to them.