If there's one main point, I think it's this from their website: "Userflow works as a layer on top of your app, containing tooltips, modals, buttons and more."
We don't "sit on top of your app." We're built into your actual app natively which makes it easier to build for both quality and any custom functionality you need.
We're taking the same developer-centric approach to onboarding at Dopt and this really is fundamentally different than the existing tools (Userflow, Pendo, Appcues, etc...).