He is a good lawyer.
Is the proper translation
Il est un bon avocat.
or
C'est un bon avocat.
or both? The article un is certainly necessary, according to this:
Si on le détermine ou on le complète avec un élément particulier (un possessif, un adjectif, une proposition relative etc.), il faut utiliser un article
But what is the correct choice of pronoun? There was a similar question, but without an adjective.