.mobi domain zone, is it worth moving?

Question

Domain name market

In less than three years, we decided to make a mobile version for the city portal. The question is what is better to use for a link to the mobile version.
- the old subdomain with the letter m
- a unique zone [domain]. mobile

Answer 1

Use a subdomain.
The new domain will not give any benefit, only harm to the SEO.

Answer 2

It's better not to change the URL at all for the mobile version.
Or do you want to spend money on a separate SEO campaign for mobile search? And so ordinary links also affect the ranking of the mobile version.