Mine is more flexible. Less assumptions about the format of the topics and payload contents. There are outstanding issues in GitHub for the GreenSky plugin that haven't been addressed, and the plugin hasn't been updated since last year. My new plugin can also connect to multiple MQTT brokers at once.
The mqttGateway plugin is even more limited in what it can do, and it's very resource intensive. It spawns a subprocess for every device that's listening for an MQTT payload, and a thread to communicate with each of those processes.
Read this thread to see how it got started:
viewtopic.php?f=316&t=22738But if what you're using works for you, then stick with it.