What a funnel actually costs to add
If Matomo is already running, the honest comparison is not "Matomo vs Tiny Funnel", it is what it costs to add a fast funnel view on top of what you have. On Matomo, that means confirming you are on a plan that includes Funnels (Team and up on self-hosted, Business and up on Cloud), then defining the sequence in the plugin. On Tiny Funnel, it means a second script tag and a click-through of the flow you care about.
Neither is a criticism of Matomo. If data ownership is the reason you chose it, that reason has not gone away, and Tiny Funnel does not compete on it. We are hosted only, and we would rather say that plainly than dress it up as a design choice.
The layer that is not in the free tier
Matomo's Community edition, self-hosted and free forever, does not include Funnels at all, which is worth knowing before you assume the feature is there. Once you are on a plan that has it, the gap narrows to speed and depth: a Matomo funnel is a report you configure, and a Tiny Funnel funnel is drawn the moment you click through your own site with the recorder on, with per-visitor journeys and per-step conditions included rather than layered on.
The short version
Keep Matomo if owning the data matters. Add Tiny Funnel for a funnel that costs one script tag and a click-through, with nothing to provision and no plan tier to check first.