You are fairly popular in one place, but another face in the crowd in the other online. It can be a total ego bruiser when you want people to like your comic everywhere, but you face the big harsh truth that different sites have different crowds. It's not good. It's not bad. It's just the way the world works. Every place has different crowds so what appeals to one, will not appeal to the other.
Then remains the big harsh question; what do you do? Do you stay in all these sites even if you're not popular in all of them? While it can be very tempting to leave, my advice is stay in all of them. I learned this a long time ago and while the lack of drawing in crowds doesn't stop hurting your ego, you have to bigger than your ego and never burn bridges.
Not everyone is going to like your work and it's not act of spite to you so don't treat it like it's personal. And also, trends come and go and crowds fluctuate. Burning a bridge is a lost opportunity even if it may not happen now. Writing webcomics takes a substantial amount of patience and emotional resilience not just to criticism, but to also facing that you're not first place every race.
And that's ok.
