Rebirth and reincarnation get conflated all the time, but the memory mechanics are a huge separator. For me, rebirth usually means the same soul in the same world, just earlier in the timeline. Think of your classic CEO regressor or a grandmaster returning to his youth. They keep all their memories, skills, and—crucially—their core identity intact. It's a second chance, but the 'you' that gets it is fundamentally continuous. The drama comes from applying future knowledge to past events, not from an identity crisis.
Reincarnation is messier, more philosophically rich. You're a new person, often in a different world entirely, who gradually awakens or inherits fragments of a past life's memories. That creates a fascinating duality. Is the protagonist the baby born in this new world, now with weird extra memories, or is it the old soul that has taken over? Stories like 'The Beginning After the End' play with this tension brilliantly. The character grapples with blending two sets of childhood experiences, loyalties, and even emotional responses. The memory isn't a clean download; it's a haunting, an integration, sometimes a battle for dominance.
The identity impact is everything. Rebirth stories are about correction and optimization with a known self. Reincarnation is about synthesis and often asks, 'Who am I, really?' The former is tactical; the latter is existential. I lean towards the existential stuff—it just gives authors more room to break a character down before building them back up.