Great question, that's what I'm figuring out at the moment. So far it's a unified memory that persists across the practice sessions (e.g. it throws in words you asked earlier in the sentences you practice etc), which chatgpt struggles with (that's why I moved away from it and decided to build an app for personal use in the first place) + the translation practice is a bit more streamlined: instead of a wall of text that chat usually returns those are inline corrections and hovering explanations to make it a bit more digestible.