In my experience, SAML seems to be a more universally used option.
Your app isn't ready to support 'enterprise' until you can do both - you'll need to use this product + roll your own OIDC or find another service like this for OIDC. Customers will expect you to be agnostic and bring whichever they prefer.
That said, the pricing worries me a bit. This is a tool we'd have to build on top of. Which means that if it disappears later because you went out of business (or just changed your pricing in some way that hosed us), we'd have a whole big, unexpected engineering project to rewrite our SSO.
And given that you're giving a hosted product away for free, it seems pretty likely that you will either eventually go out of business or change your pricing.
I know it sounds silly, but as someone who'll probably have to add SSO to my current project in the next 6-12 months, I'd be a lot more comfortable betting on you if you had a sustainable-sounding paid tier other than "free for now" and "idk email us." It'd certainly make it easier to pitch to the rest of my team. :)