Innocent Sin (PSP) is piss easy. I used autobattle for every single random encounter and never switched my characters' Personas (aside from when they evolved), yet I didn't die once throughout the entire game.
That said, the story is A+, top notch. It's absolutely worth playing.
Eternal Punishment (PSX) on the other hand is actually challenging in its gameplay, you'll need to take advantage of negotiations and actually make new Personas and stuff. Story is also pretty solid stuff. Both recommended.