I'll speak a bit to the language audience, and others might weigh in as they see fit. The target is pretty broad: Unison is a general-purpose functional language for devs or teams who want to build applications with a minimal amount of ceremony around writing and shipping applications.

Part of the challenge of talking about that (the above might sound specious and bland) is that the difference isn't necessarily a one-shot answer: everything from diffing branches to deploying code is built atop a different foundation. For example, in the small: I upgraded our standard lib in some of my projects and because it is a relatively stable library; it was a single command. In the large: right now we're working on a workflow orchestration engine; it uses our own Cloud (typed, provisioned in Unison code, tested locally, etc) and works by serializing, storing, and later resuming the continuation of a program. That kind of framework would be more onerous to build, deploy, and maintain in many other languages.