If there is only 1 message per packet, it's only 1 byte more to send, but the multiple message feature allows you to have the packet sending on its own time interval, which is very important. With a single message per packet you could only send 1 message per interval, but with multiple messages you could send all messages which happened during that interval, so there would be no huge delay between messages if the interval is set to 5 seconds.
If you want to make it even more advanced, you could tune the interval according to the network latency. If there is no latency, the interval would go down, and if there is high latency, the interval would go up to prevent total overload of the network connection.