If he is a smart lad, he should definitely consider leaving at least on loan although I'm not a fan of sending our players on loan myself.
Leaving on loan is a very risky choice especially for La Masia canteranos because they have become accustomed to one style of the tactical system which is possession-based Cruyffian football for many years.
But Puig is already 20 this year, he must not waste his time with the B team and should look for more competitive football. Whether he stays with the B team or wins the full promotion to the first team, it is obvious that he will get even less playing times than Aleñá this season. Not to mention that he needs to play under that fucking Shitverde who is total garbage in terms of developing players.