Hello matt819!
The difference between certificates depends on what the certificate provider offers for warranties, browser compatibility, and more. As an example, I included the specs for a popular SSL certificate provider Comodo.
EV SSL Certificate
Fast issuance and validation
2048 signatures / 256 bit encryption
Trusted by 99.9% of browsers
Unlimited Server Licenses
Industry Leading Support
30 day money back guarantee
Free TrustLogo boosts conversion
$250,000 Warranty
You can get SSL certificates for more than one domain for the certificate. These are called Wildcard SSL Certificates. You can reuse a Wildcard over and over for more than one domain.
What it boils down to with a standard SSL certificate is if its 2048 / 256 encryption, a good warranty for compromised SSL data, and ease of purchase with no hurdles.
Best Regards,
InMotion