RESTful API Create - should it return conflict if exist, or be idempotent and return 200 if values are the same?

What title says - if I have an endpoint to create element, but the element already exist, what's the best / common practice? Should I:

• Return conflict based on the fact that an object with the key already exist?
• Or check if the existing object is the same, and if so return 200 instead (or other ok-ish status code)?

Thanks!