Thank you for article, it's a great introduction to HTTP/s! Didn't know that HTTPs preferred by search engines but it sound logical.
Wanna add a couple of comments based on my experience: – The speed is basically the same. Latest version of TLS is lightning fast and supports TLS session resumption even if TCP connection is dropped. A small research – keycdn.com/blog/https-performance-overhead. – HTTPs also allows to verify client identity with client's certificate. Yes, it's a rare case, but it's possible. Might be suitable for back-2-back integrations.