I've caught both. Here in Iowa we are at the northerly edge of the range for Redears, and we are at the southerly edge of the range for Pumpkinseeds. The Redears I've caught are INCREDIBLE fighters!!! Plus they get bigger than Pumpkinseeds. Love those things!
Both have red on the edge of the gill opercle. Redears don't have the iridescence on the sides like the Pumpkinseeds...the Pumpkinseeds are much more colorful.
This is a Redear I've caught: