Much better radar, much better asdic, a far superior ASW weapon in the Squid,
Many of the Japanese escorts or even fleet destroyers did not have radar in the early part of the Pacific war which was more than a bit late by European standards.
The Japanese asdic was several generations behind the British and the gap increased. It also did not not help that some of the late Japanese escorts were noisy.
About as advanced as the Japanese got for ahead throwing weapons was a single 80mm army mortar mounted ahead of the Bridge. This arrived late and obviously was not very effective.
While the British Hedgehog showed up in late 1942 poor training delayed it's use for quite a number of months. Crews did not have confidence in it's ablities or proper training in use. There as a lot more too it than point the ship at the suspected area and fire away.
However the Japanese never even got close even in 1945.
A lot of British or American hunter teams used one or more ships to 'fix' the subs (locate and track) and would then use the radio to coach the firing ship into position. The ships own asdic would not point down enough and the target would be lost on the attack runs. If the first run did not work they would often swap and one of the trackers would make an attack run while the first attacker reloaded it's launcher/s while providing asdic support for the new attack ship.
However this also needs practice, training and good voice radios. This was also going into 1944.
The Japanese in late 1941 were behind, well behind, where the RN was in late 1939 as far as ASW.
However in a somewhat similar historical pattern the numerous (by Japanese standards) escorts don't show up until 1944-45, leaving most of the early war work to be done by a few handfuls of converted destroyers, steam torpedo boats and patrol boats. And in 1942 few had radar, not all had Asdic, DC storage was small and so on.
Much of the ASW was done by fleet destroyers "on loan" in the first part of the war as
they didn't have enough escort ships.
In April of 1942 the were only two escort groups (this is after all of the early conquests')
The 1st escort group had 10 old destroyers, two torpedo boats and 5 converted gun boats for the Japan to Singapore route.
The 2nd escort group had 4 old destroyers, two torpedo boats and 1 converted gun boat for the Japan to Truk route.
There were a few other odds and sods but obviously they needed fleet destroyers to fill in. And that leads to poor training or team work. The Japanese never had a ASW school. In fact some of their escort commanders (late in the war?) were from the merchant marine academy and not the Naval Academy and we can imagine how well that worked in mixed groups.
The RN was not perfect but the distinction between the regular navy and "wavy navy" was probably the least marked in any navy.
