The short version of EPDM fs PVC:
EPDM started the single ply business over 40 years ago.
EPDM is a Thermoset product, meaning that it is a cured membrane. What you see is what you get for its lifetime. Because it is thermoset, you use a special tape to put together the seams.
EPDM has no chlorine or plasticizers, thus is environmentally and applicator friendly.
PVC is thermoplastic, meaning it is welded by using hot air.
PVC is polyvinyl chloride, meaning it has chlorine, plasticizers and other chemicals that make, basically, a hard plastic into a flexible membrane.
PVC is an uncured membrane and cures over its lifetime.
Some environmentalists claim PVC is bad for the environment in any form. Who knows?
A new product called TPO is replacing PVC in the thermoset market because it does not contain chlorine or plasticizers and is more environmentally friendly. It also uses hot air to weld the seam.
In the overall scope of single ply roofing, EPDM is the largest selling membrane in the US by a huge margin.
Lastly, EPDM is black in color and PVC is white. In sun belt states the white membrane is preferred. In your area the black roof is the better option.