Peace be upon those who follow path of true guidance!

Respected Language learners(teachers/students),

                                                  Which medium or tool or application you believe is the best so far? I mean let's say you found a language partner online on any language website (e.g. italki) and now you want to learn, which one will you choose and why? Please give atleast a 2 line detailed answer.

1) Skype calls (video or audio or just chatting)

2) Whatsapp or LINE

3) italki quiz or exercizes or notebooks etc