I haven't heard of working dc in a spiral to make a tube (not that it doesn't exist, mind you). I would think that it would look somewhat skewed because of the height of the stitch; something that isn't as noticeable when working sc in a spiral.
If you're going to join every round, which is probably what I'd do, you going to want to pay attention to your "turning chain". If you do the usual ch3, it could be quite noticeable depending on the yarn you're using and how tightly/loosely you crochet.
For a while, I was doing ch2 instead of ch3 for my dc turning chains because they seemed to stick out less to me. Then I discovered this: http://www.youtube.com/watch?v=3LxYpo-tyi8
which can be tricky to learn, but well worth it; this stitch blends in very well!
If you were going to do it in a spiral, I imagine you'll need a few "height building" stitches to start with, to make your bottom edge flat instead of having a step. Perhaps sc, hdc, dc, and then dc around? If no one else pipes up with a another suggestion, you might want to experiment with this a bit before starting your project.
You'll need some extra stitches at the top of the tube, too, and for the same reason. Probably dc, hdc, sc, or something like that.