[SandyCaesar]

Actually, surface ships are too easily detected. While a frigate at 5kts might be as quiet as a sub, at 15kts it's far noisier, and at 29kts everyone in the area knows he's there. Plus, surface ships have less sensor capability than subs: their towed arrays aren't as good as submarines, and their bow array...let's just say that it isn't nicknamed the "Helen Keller" for no reason. Then there's the question of RORSATs and air recon: unless you're in completely friendly waters with total, 24/7 air cover, surface ships are vulnerable to other forms of attack. Their only real advantage over subs lies in their helicopters, but in many cases a submarine can whistle up an Orion or a Nimrod if it has to.

As for aircraft, their biggest problem is endurance. While an Orion might be able to loiter on-station for 14 hours, subs can sit and wait for weeks on end. Buoys, too, are not as capable as a 688/T-Boat/Akula's towed array, and they have a relatively short lifespan.

So it all boils down to stealth, endurance, and sensor capability. In the first and the last subs have air and surface platforms beat; as for endurance, a surface ship might be able to match a submarine, but it isn't nearly as stealthy. Nuclear subs are quite fast, and diesels can get to place to place without too many problems in a given patrol area, so speed isn't really an issue. Plus, surface ships also have the same "spent" issue as submarines. The enemy sub can't do more than snapshot and hope to hit if he's fired upon early enough, and if he dies it could be a while before his government knows. In the end, subs are the best ASW solution, mainly because of their stealth.