When comparing these two products, the main differences that stand out are cost, plan limits, and included features.
Formcarry's monthly plans start at $20/month with a submission limit of 2,000. Compare that to Submit JSON's hobby plan at $5/month with 2500 submissions. That's 1/4 the cost. And Submit JSON's $15 dollar plan gives you 5x the submission limit.
Hate to say it, but Formcarry simply copied Formspree, right down to the logo. They fall short where Formspree falls short. You should check out how Submit JSON stacks up aginst Formspree, as we have very different design philosphies.
Which is the best form backend for you? We think the answer is obvious, but we'll let you decide.