Henry,
My memory is that when you do textured lineart with the Watercolor brush, you bump the res up so the tool reads as an ink tool better. Is that true? How big is your canvas here, and how big do you use the watercolor tool for the linework?

I agree that the Watercolor and Felt Pen tools are the most "realistic" IMO. They interact with the canvas texture. I guess there are comic artist out there who use Bristol board and what not, and want a really smooth line, like what the Ink Pen offers, but that could be just as easily accomplished with the Watercolor tool by just removing the canvas texture. Of course, the Ink Pen also offers smoothing, but I don't really care for that look. A bit too clean to me. I like to see the imperfections of the human hand at work when I look at a painting. That's the way "in".

It's all a matter of preference, but regardless, I like where you're going with these things.