While HTTP is a good choice for displaying information only once, MQTT is the solution whenever you want to enable communication (exchanging messages (data) ) frequently.
MQTT points out its ability to hold connections open and its way of handling data formats. Both enable successful, reliable message transfer.
On the other hand, if you do not exchange messages frequently, HTTP should be your choice.
keep-connection-open vs request-response
MQTT is superior to HTTP if you have devices that communicate regularly. The MQTT protocol can keep a connection open for as long as possible, sending only a single data packet. Unlike HTTP communication, which requires you to open and close a connection (including TCP) for every data packet you want to send, you can significantly reduce CPU usage.
HTTP relies on text. Base64 encodes and decodes any binary code，creating more workload for the CPU。 An MQTT payload can be any type of data – encoding is not necessary。