A cupsole is a cold process sole that wraps around the shoe. Cupsoles are sturdier and generally provides better stability and protection and greater cushioning when landing from drops. Cupsoles are also thicker and more durable and wear-resistant. If you’re a skater who is constantly suffering from bruised heels, you’ll probably want to go with a cupsole. Cupsoles are usually less flexible than Vulcanized soles and don't offer as much board feel.
Vulcanization is the chemical process of curing rubber from a soft, elastic state into a solid, stronger state. Generally, a Vulcanized sole is thinner, flatter, sandwiched with a midsole, and glued to the upper and surrounded with a "foxing" tape to hold them together. Vulc soles provide more flexibility, better grip, and increased board feel. As a general rule, Vulcs are less bulky, too.