What are some alternatives?
When comparing ClickSSL and Comodo, you can also consider the following products
Let's Encrypt - Let’s Encrypt is a free, automated, and open certificate authority brought to you by the Internet Security Research Group (ISRG).
Digicert - Encryption & Authentication
SSL2BUY - SSL2BUY is the foremost SSL certificate provider of online security solutions for businesses.
GlobalSign - GlobalSign offers a range of SSL Certificates with the strongest 2048 bit encryption and value add features to ensure your website is protected.
GeoTrust - Guarantee online customer security with SSL certificates from GeoTrust. Purchase in bulk, manage multiple certificates & become your own Certificate Authority.
SafeCyberSSL - SafeCyberSSL is a platinum partner of leading Certificate Authorities.