[alwayslikethis]

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.

[melagonster]

I can understand pay for supermemo, but it is not in list.