I like the Cintiq models because you are working right on the image. Any Wacom product handles smoothly and the pen response is fine. There are a couple pen models with different grips.
I do very well with the smaller Cintiq, but the 21 inch model is probably preferable to someone with more complex 3D projects.
You can get some deals on ebay, but $1500 is the minimum I have seen for this model. (sigh. I am saving my $$.)