I have used Jin Bu Yi inkstick, and I feel yes, it is smooth enough for me and deep black. I have not used all the premium inksticks myself but the feedback is quite good. There are differences in each inkstick’s recipe, however, as these recipes are confidential, it is difficult to indicate it clearly on our website.
Actually Jin Bu Yi is the most popular of all with professional artists, see:
My first inkstick was (just ordered yesterday) the small Jin Bu Yi Fine Oil Soot Black Inkstick. I chose it both for the shape and because one review said it worked so well for dip pens. Since I hope to use it with both glass and steel nib dip pens for drawing and my poor calligraphy it seemed a good choice. This morning I walked out behind our house and there was a huge owl sitting in our plum tree. He was the first I have ever seen here. I took it as an omen that I had chosen wisely.