As someone who has both practiced lean startup methodologies, as well as someone who values their own time.

Go with the small startup's API until you have other resources other than yourself who can develop better than you can. It's just not worth getting tied up reinventing the wheel when it si your job to defer, outsource (elance, odesk, freelancer.com, guru.com, gun.io,) or lisence their code. Your responsibility is to move the company forward in big steps toward its core mission. Not tackling something because you think you could do it.

If you would like to discuss this further, give me a call. On the house.

When you wake up in the morning, say to yourself "Get to that MVP" 3x. Saying that would make the answer to this question a no brainer!

Good luck!