Excellent Work LES! I've only been here a few days and this one post helped me immensely. I've been considering quite a few of the rounds you tested, and this helps make choosing easier.
I'm brand loyal when it comes to ammo, and have always used Winchester or Federal in my handguns and rifles. I'm pretty much doing the same with my 590. I've picked up a few boxes of the Winchester PDX1 Segmented slugs and Super X 00Buck. Going to be on the lookout for some of the RIO, if it's still made. Would be a good, inexpensive alternative.