I'm the most comfortable reading and posting on Ao3, but I dislike commenting on Ao3, so I for the most part read on Ao3 and then comment on DW (in your case when it's posted in both places) and then don't comment at all on other authors. I will read fic on tumblr but I don't like how easy it is to lose, when on Ao3 it's easy to find fics one remembers. I love that it is truly an archive of our own, I feel like as long as the people whose work I care about post there I will never lose anything ever again.