Difference in the Domain Selection for Checkout URL

The Checkout URL found at Setup > Site Builder > Setup Website > Setup tab contains 5 selections:
 

• checkout.netsuite.com
• securedcheckout.com
• onlinecheckout.com
• webstorecheckout.com
• suitecheckout.com

There are webstores that uses other checkout urls aside from checkout.netsuite.com for them to carry their own branding. 
The checkout.netsuite.com URL uses Extended Validation (EV) while the other 4 URLs are using Wildcard SSL Certificates.

Extended Validation is a special type of certificate which required more extensive validation before the SSL certificate is issued.

Wildcard SSL Certificates helps enable SSL encryption on multiple sub-domains using a single certificate as long as the domains are controlled by the same organization and share the same second-level domain name.

The additional benefit that EV gets is the "Green Address Bar" as indicated in this website http://www.verisign.com/ssl/sss-information-center/ev-ssl-certificate/index.html (website for additional SSL information ).