It seems like the only way you'll be satisfied is if you try a JNS Kato and compare it with the one you got from the other vendor. Kato's standard line may be geared to perform one way, while Maxim's line has some changes which he feels are an improvement. Different strokes for different folks.
Anyways, if I were to get one, I'd get it from JNS. I trust Maxim enough to believe that his Kato, for me, would perform better than the standard one. Plus, JNS ones are cheaper and sport a sexier steel.
I'm not dissatisfied at all with anything. Just an opinion. But you're right. Only way to know is try both