Which is a correct sentence?
It is comfortable living in Japan.
It is comfortable to live in Japan.

What difference is that ?

Question

Which is a correct sentence?
It is comfortable living in Japan.
It is comfortable to live in Japan.

What difference is that ?

Answer

Both are proper and fine. However, if I were saying that sentence, I would probably say "Living in Japan is comfortable."

Answer

Both sentences are fine.

While the second sentence is more general, the first one could also be referring to a living creature (The "it").

Answer

Both are ok.

comfortable + gerund

and

comfortable + [full infinitive]

are both OK in your example. But this isn't always true of adjective + gerund/[full infinitive]