Mt Cuba Center has been comparing native perennials in trials since 2003. Studies have included Asters, Echinacea, Heuchera, Coreopsis, Baptisia, Monarda and, most recently, Phlox. Each study compares a variety of species and cultivars. The plants are evaluated for their observed ability to attract pollinators, ability to resist disease, length of bloom, habit and form in the garden as the season progresses, and overall appeal as evaluated by garden visitors. These are excellent studies, easy to read, and chock full of great information for the avid native perennial gardener. Link: Mt Cuba Center Trial Reports.
If you live in the Annapolis, MD area or on the Eastern Shore, this list might be useful to you. These are places I routinely check, to find the natives I need for landscaping. Link: Where to Buy Plants pdf