I mirror on Webtoons, Tapas, and SmackJeeves. I have about 10x the number of readers on both Webtoons and Tapas than on SmackJeeves.
Due to the low traffic, I keep wanting to stop mirroring on SJ, especially since I have to process my files differently for there than for Tap or Webtoons. But I have some regular commenters there, and the SJ mirror is really well-indexed by Google for some reason -- it's the first result when you search for "Camellia comic", whereas my Tap and Webtoon mirrors don't show up in search results at all. For those two reasons (and because I met a good friend on SJ), I haven't bitten the bullet yet.