The PLAN has two types of nuclear attack submarines in service: the Type 91 (Han class) and the mysterious Type 93. The original Han submarines were notoriously noisy boats with poor radiation shielding, literally being a greater hazard to the ship’s own crew than to any reasonably competent warship or submarine. It is now being replaced by the Type 93, but those Type 91 submarines remaining in service have received upgrades, with new sonars and sound-absorbing anechoic tiles. The submarine has a submerged speed of 25 knots, surface speed of 12 knots, and can use 533 mm torpedoes and mines. Han submarines can also fire Silkworm anti-ship missiles, but they must take the dangerous step of surfacing first in order to launch the missiles.
The new Type 93 (Shang class) is, unfortunately, too shrouded in mystery to comment upon. The only thing that is certain about this new submarine is that it is superior to the Han class in every way. It was originally thought to be based on the Russian Victor III class submarine, but this is unlikely as the vessel looks nothing like the Russian boat. It is thought to incorporate modern hull and screw design, advanced sonar and quietening techniques, and come with six 533 mm torpedo tubs and the ability to launch missiles while submerged. Past that, predictions of the submarine’s capabilities range from being an improved Victor III to a rival for the Akula.
The sole operational class of nuclear attack submarine in the Indian Navy’s inventory is the Russian-made Akula. The quietest of Russia’ nuclear attack submarines, the Akula uses quieting technology derived from Japanese and Norwegian industrial technology sold to the USSR in the 1980s. The Akula class is believed to be able to dive to depths of 2,000 feet, achieve submerged speeds of 33 knots, and mount the best sonar the Russians have, as well as being armed with six 533 mm torpedo tubes.
The Indian Navy is also testing its first home-grown nuclear attack submarine, the INS Arihant, but this vessel has also not entered service yet.
In terms of a straight comparison of different vessels, the Indians win on the basis of their use of what constitutes the pinnacle of Russian hunter-killer submarine design. By contrast, the Chinese Shang class submarine is roughly equivalent to a less capable submarine, and it should be noted that the Shang is thought to be heavily based on imported Russian technology in the first place.
However, it should be noted that while the Chinese subs are inferior, both submarine types are homegrown designs. The Chinese have more experience in this department than the Indians, are liable to catch the Russians in their next generation of submarine, and at that point it will be the Indians who have a lot of catching up to do.
Sources: timesofindia.indiatimes.com/india/Russian-Akula-N-sub-handed-over-to-India-homeward-bound/articleshow/6384881.cms; globalsecurity.org/military/world/china/type-93.htm