One thing that Anki does very well (and that neither memrise nor duolingo attempt) is allow you to immediately rate the difficulty of an exercise right after yo

One thing that Anki does very well (and that neither memrise nor duolingo attempt) is allow you to immediately rate the difficulty of an exercise right after you do it. This allows you give feedback that e.g. You got something right by fluke or conversely that you got something wrong because it was so easy you weren't paying full attention. I find with memrise that it sometimes repeats the easy stuff too often leaving less room for hard stuff that I 'fluked'. Also Anki allows you to fill your brain with the subset of the universe of vocabulary that most interests you (knowing that pinguna is a macchiato made my life a lot better today). I'd advise starting out with the set courses of memrise and duolingo and using them to fill up an Anki card set as you come across interesting vocab.