The Japanese ships are not that good, mostly because they are direct copies of earlier American versions. Ours is more advanced, it is smaller, only because the roles are different.
52D is not suppose to be the tip of Chinese naval power, it's a support ship to bigger DDGs not built yet.
Also Japanese ships are severely restricted in offensive capabilities meaning it lacks offensive punch. It can only defend, not only that it was built as a complement to American battle groups so it cannot effectively do battle without America.
If America pull out or doesn't participate, their ships are just huge floating targets with not much use. But it does have better anti missile abilities than China, at least on the seas, and only at this moment, that will change soon.
I also agree that Chinese VLS is way more advanced, but then we also designed it way later than the Americans did, the new American system on the DDG-1000 is better, but that's not for export.