You're better off comparing with Pokemon. You capture and make a party of demons with various skills. As far as the Persona vs. SMT difference:

SMT: 1 hero, who is an active battler himself, and a party of captured Demons.

Persona: A party of allies, each with one Demon/Persona bound to them, which (after Persona 3) grow in strength as you deepen your bond with your allies. The main hero is a "Wild Card-" while they do have a default Persona, they are able to switch their Persona in battle. In 3 and 4, demons can be more of an item drop, but 5 brought back SMT's negotiating system since the enemies were the Demons themselves rather than generic Shadows in 3 and 4.

You're better off comparing with Pokemon. You capture and make a party of demons with various skills.