When a Bluetooth WiFi Gateway sends data to a server via HTTP, the gateway has to connect to the server to start a connection and then use that connection to send the data. The connection part starts a new TCP connection with handshaking. Starting a new connection every time data needs to be sent to the server uses network data and creates work for the server.
Some gateways such as the IGS01s have a ‘keep-alive’ setting that allows the connection to be re-used across HTTP requests. This reduces the amount of data used on metered networks such as cellular, reduces possibly metered data throughput at the server and also reduces server loading thus improving performance.
Having said all this, you should consider MQTT if you are really concerned about efficiency and performance.