The verdict
For a developer-led software team that sells globally, I'd pick Polar. Usage metering, a sandbox, a migration guide from Stripe and an official MCP server that signs in with OAuth suit how those teams work. It also does not carry the ownership question that Lemon Squeezy does.
If you are a creator or small seller who wants licence keys, secure downloads, upsells and email in one product, Lemon Squeezy fits that better. Either way, read the vendor's blog on Stripe and Managed Payments before you build on Lemon Squeezy. Compare fees at your expected volume, since the cheaper option changes as you grow.