Sometimes there is a visible difference. Switchgrass can vary in height from 2 - 3 feet up to 8 to 10 feet, depending on where it is from. However, the real reason to care about local genetic strains is that local strains have genes that adapt them to local climate, soils, etc. Little bluestem grass from Texas may not do well in North Dakota.

People who care about saving the full diversity of species that God created and/or evolved also care to save the ecosystems that were created/evolved as well as the genetic strains that were created/evolved. Modern conservation biology seeks to conserve the diversity of life at all levels from ecosystems to species to genes.

Are there unique aspects to local types in your area? Yes. Are they disappearing? Probably. Are they worth seeking out? I think so. Are the differences visible? Sometimes.

After reading your post, I am confused after reeding your seed want list. Some of the seeds you seek are not native to western MI. If I'm wrong correct me.