For me, it has to be Persona 4. The reason is because social-links with the individual party-members can actually influence how they perform during battle, as well as Rise's ability to scan dungeons and enemies. When their s-links max-out, their personas evolve, magnifying their strengths, nullifying their weaknesses, and symbolizing their users' growth and development as characters.
Not so much with Persona 3. When playing as a male protagonist in the original, P3: FES, and P3P, you only have access to your female party-members' social-links. But, even as a female protagonist, where you can access both males' and females' social-links, you can't influence and increase their battle performances through those s-links like you would in P4.