There is a technology limit, here. IMHO at this point, at least available in the market for us users, there is nothing as accurate as traditional pencil and paper. That said, the bigger the tablet size, the most accurate. I would only use Wacom Intuos, if I'd were to use any tablet. (I do , indeed.) You get more accuracy with an intuos than a bamboo, and more with a bigger intuos than a small one. Now, some people find counter productive a too big sized tablet, as they can hardly have at same place keyboard, mouse, tablet. A good compromise between price/accuracy/space, might be the M intuos size. I would not go for S, nor a Bamboo, if were shooting for accuracy. I'd go for M,(surely not the "Wireless" model) L or XL.
That in case you are comfortable with the tablet's style of drawing. Some people can't and aim for a Cintiq. I am a traditional artist that became digital so long ago, than these days I am more used to typical digital tablets. I'd skip the Cintiq(I own one, and several intuos), pretty expensive, and aim for a large Intuos size. Cintiq have some bigger lag, imho, there's the calibration problem, certain accuracy loss around borders (worse in 12" models), it's based in intuos 3, not 4, and they are non proportionally expensive, compared to the good service a regular intuos does.
There are other solutions, or better said, helpers, that you can add to the advantage of a big Intuos. Softwares can do an average of your stroke, so less trembling is produced in the stroke. A lot of this trembling is not produced by your hand, as you know you can produce firm lines in paper. Is mostly a technology limit. So, softwares do that averaging, which you can fine tune in preferences, or brush settings. This can be done in Illustrator, somehow in Flash too, but also in a free software for drawing called Mypaint.
(I think I already answered to this, but is ok for me to answer again, because is not the exact same question, and I have changed my conclussions since then, after several new experiments and experiences.)