The biggest difference would be that GitHub Sponsors has no fees [1], so everything people put in will go to the developer. Where Patreon can take 5-12% depending on the plan [2].
Additionally, GitHub is just so much closer to the actual open source work and more easily discoverable for users of your product.
As a supporter, I'll pick GitHub over Patreon anytime.
It's a promotional incentive. Fees will happen, and matching will end. But in the meantime, it means my sponsoring a project I care about magnifies my money for a cause I value, so I'm happy to participate.
Additionally, GitHub is just so much closer to the actual open source work and more easily discoverable for users of your product.
As a supporter, I'll pick GitHub over Patreon anytime.
[1] https://help.github.com/en/github/supporting-the-open-source... [2] https://www.patreon.com/product/pricing