Realistically none of them are full fledged alternatives to Anki. What Anki provides: - Open source guarantees your data won't be gone and/or unusable when th

Realistically none of them are full fledged alternatives to Anki. What Anki provides: - Open source guarantees your data won't be gone and/or unusable when the company goes bankrupt in a few years - General purpose, fully customizable card creation - Tunable scheduler, recently also fully tunable scheduling systems like FSRS.