Copper certainly has better thermal conductivity, that is a fact, but so much more goes into it than that. Fin design, space between the tubes, size of the tubes. Even with all that, a radiator isn't there to radiate, it's there as a heat sink for air to flow over, so IMHO, yes unpainted copper is about 40-50% better at simple heat conductivity, but I think that difference is a smaller component to the mix over air flow. They may even be closer to each other when slathered with thick black paint
I have used all kinds and never saw the real heat problems until living in Vegas, and there, it was more about airflow than radiator material in my experience.
As far as the Flow Koolers, I do think the original was just a plate to buy with 3 rivets, then the pump came pre-modified with the plate, but as I understand they have gone beyond that now, as shown by the pictures and Mike's comments. They look pretty good, but I also haven't had any issues with Edelbrocks either. Another thing to always look at is pulley ratio. 1:1 minimum on most street cars, and depending how high you spin it, overdriving the fan and pump can be a benefit too. Rarely is slowing it down a good idea