I'd say blogger would be the best for an art blog, tumblr just allows people to reblog your work without sourcing it all too easily, which I think is quite risky. Tumblr is good, but mostly for just sharing things.
Also, if you want an online portfolio, we've been recommended a website called carbonmade, so maybe you could check that out?
I use Flickr for my art gallery, just something to throw at the family when they want to see my art. (No way in hell would I link them to my dA aha) Don't know if you are going for just a portfolio, or a blog as well. Blogger is nice too, if you need a blog.