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
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.