This gives a random trycloudflare.com subdomain each run, the other requires a domain and tunnel key on your account.

From their docs [0]:

> Free tunnels are meant to be used for testing and development, not for deploying a production website.

[0: https://developers.cloudflare.com/cloudflare-one/networks/co...

As far as I can tell, the difference is that they made a new website? The cloudflared instant tunnels have been around for years, including json output as far as I know.