What are the best places to get a SSL/TLS certificates?

The fatal flaw of a Certificate Authority is pretending that they can be trusted. Individually, they can, but as a whole there are always CAs that are controlled by state actors or subverted by bad guys, and by using them you are betting that any abuse is discovered and handled quickly by the community. Running your own CA is placing trust only in yourself - you are not relying on a third party to vouch for a given certificate. That can be invaluable, or worthless, depending on your need.