I've stopped posting art on deviantart simply because the community just . . . sucks. Plus the staff is awful. Most of the art on the front page these days is fetish bloat art and other softcore-porn stuff that hasn't been marked NSFW, when it really SHOULD be, and none of the staff members are taking strides to stop it when it's clearly a problem and so many people have been complaining about it.
The same artists are showcased and loved every day, and with such a large userbase, it's very difficult to actually get your foot in the water let alone get your feet wet (unless you're one of the artists that caters to DA's community, in which case, all you draw are adoptables, crappy teenager-quality sonic art, bloating fetish art, and high-quality pics of your ass in lingerie u o u).
Tumblr's alright as long as you know how to properly use it and don't sell yourself out to the "I'll follow you if you follow me!" trend. I think the only artists I actually follow on there are Min, Sarah Anderson, and Rickard Jonasson. It's also really easy to get caught up in the drama and bullshit that is everywhere else on Tumblr if you're not careful
But it can be a good place to host your stuff, so long as you don't associate with the wrong crowd and know how to take full advantage of the filter system, and are willing to update often.
I used SmackJeeves shortly before coming here, but was just never satisfied with it. It's got a very . . . how do I put it . . . juvenile set-up to it? As in the actual website's layout and design doesn't really make your comic look too good in hindsight. Plus it's a lot of BL and yaoi comics, 'cause that's just the audience they happen to cater to, so if they're not your thing, you might have a harder time making an influence on readers. Also, some functions on the website require payment to use if you want to use them, vs. Tapastic which will actually pay YOU just to draw and there's nothing locked off (except for supporter-locked content, which is reasonable because it goes to the creator anyway).
I haven't used any other comic website since finding Tapastic, but before then I used DA, SmackJeeves, Tumblr, and my own website. When I found Tapastic, I slowly started to just stop updating on other sites, starting with Tumblr (never was really active with it anyway), then SJ, which wasn't bringing me in any readers or views at all in comparison to Tapastic when I joined, then eventually shut my own website down cause it was costing me more money to own than it was actually making me, and then eventually, DA, when I realized that the community and atmosphere didn't have anywhere to go but down.
Tapastic is my favorite place to be and I hope it stays that way for a long time 