I hear tell that the UK Astute class of Nuke is quieter than - or as quiet as - the top-of-the-range German Diesel Dolphin-class.
With stealth-tech converging between Nuke and Diesel I think the real advantages of Diesel are numbers and price - as opposed to speed, capacity and endurance.
That would be interesting....
But the greatest vulnerability with any nuc boat will always be that it has a belly FULL of rotating mechanical machinery...hundreds of pumps and motors, just waiting to make a noise transient. Even with the best, most modern sound isolation technology, I don’t see how that can compete with a submerged diesel on battery, where all you have running is the electric motor (very quiet), maybe some pumps for shaft sealing water, and ventillation fans.
Of course all the technology in the world is useless without a highly trained professional crew, and on that level, the US has no equal.