What a nice clickbait title. A is better than B, even though A is an apple while B is an orange, and we use them for entirely different purposes. Some functionality provided by Heroku can be replaced with Docker, and some missing features of Heroku are in the Docker infra, that can be added to Heroku using software (like service discovery: https://blog.heroku.com/managing_your_microservices_on_herok...)