anki or quizlet?

It depends on your learning style I think! I've used both of them a bit. Anki is really good, but it very heavily depends on you using it every single day as it's based on spaced repetition - otherwise the flashcards build up, it becomes a bit overwhelming (for me at least) and the effect of the spaced repetition is lost. I've used Quizlet consistently for about six years now, and although it's gone downhill a bit (some features that used to be free like write mode are now subscription only), I'd still really recommend it. There's lots of different options for how to review your flashcards, and it's not time-based like anki so it's much better if you need to cram quickly (ideally you won't of course but sometimes it does come to that)