When I asked my builder which radiator to buy, he told me buy anything but the Mishimoto.
He referred me to Fluidyne, Champion, and I forget the other name but they were custom made per order.
I ended up with a 3 row Champion and much like you I saw lower temps. I had an OEM style radiator in there originally though. My temps went from 214ish to 185ish.
I replaced a leaking Fluidyne with a Mishimoto about 9-10 years ago. I haven't had a single problem with it.
Certainly, enough time has passed since then that their quality may not be what it once was.