Creator of Empire here. Empire and Convox are kinda like brothers and sisters, both really similar in implementation and philosophy. There's a couple of subtle differences, like how Empire expects that you've already built a Docker image somehow, whereas Convox can just take some code and do it for you (hosts it's own docker registry). Convox also supports streaming logs, which is pretty awesome (although, coming soon to Empire too :)). Convox is a little more reliant on AWS, whereas Empire was designed to be able to work with other backends like Kubernetes for example (not implemented yet). I would say, use which ever one best suites your needs, they're both great, and like David said, we talk a lot and share ideas back and forth.
