New domain or subdomain for the service?

Question

Search Engine Optimization

There is an idea for a completely new revolutionary service (this is to attract attention), it is partially implemented.
There is also a site with a service that is already running and has good traffic, but the concept and idea have nothing to do with the first idea.
So the question is, do a new project on an existing site in a subdomain or subsection?
Or run on a new domain and re-roll for a new service?
What are the pros and cons of these options? What will start faster, and will there be a negative effect on the existing site if implemented using the first method?

Answer 1

each on its own domain, and link to each other (example habr, geektimes, toster...)

Answer 2

Personally, I would run on a new domain, adding a link to a new service in the menu on an existing one. An example of Toster, Habrahabr, Geektimes is a great solution in my opinion.

Answer 3

I would probably start a new project on a different domain, for example habrahabr, toster, geektimes.

Answer 4

And if there is a need, you can work with VPS. There is an interesting company on this subject swiss-vps.ru