You want ocean escorts, but since the Cold War ended, there hasn't been a need to buy or have ocean escorts any more. There aren't any large force of enemy submarines. This world has grown up, the UN seems to be working well.
The US Navy has never considered ocean escorts, frigates front line warships. The US prefers to have cruisers and destroyers escorting their carrier battle groups, urgent replenishment groups, and their amphibious force groups.
The US Navy have found their former frigates wanting. They are either over armed and/or too deep in draught for coastal duties. We have also found our minehunters wanting, one must use a cargo ship to move them half way around the world. We want a ship which can carry Marines and SEALS, their small vehicles around to scout the enemy and engage the drug cartels and be capable of doing mine hunting and ocean escorting too as a secondary concern. Therefore, the LCS.
The US Navy has plenty of cruisers and destroyers carrying much more surface to air missiles than frigates, not to mention Harpoon and Tomahawks, much less 127-mm guns. Do ASW ships in the middle of an ocean escorting commercial cargo ships need them against stray aircraft and missiles. All that is warranted for LCS are self defensive missile systems, including Vulcan Phalanx CIWS and RAM. Plus a gun large enough to take on patrol ships.
Contracts for the second ships of both have been awarded lately. It should be interesting which ships will win the big order.
Frankly, I like the Lockheed ship the USS Freedom with its deep vee hull form.
Littoral combat ship - Wikipedia, the free encyclopedia
Here is a link to Austal's multi-purpose ship similar to the Independent LCS. Play the video.
Multi-Role Vessel - Austal