wacom is usually the way to go, but it's more about the software then the input. not all of them give good results to make a painting. from there it's all about skill, since your looking at the screen and your tablet is flat on the table, it may take getting used too. if you get a large tablet, you get more fine detail, but you also have to move your arm more to get across the screen. the smallest one usually has the fewest features, i usually get a 6x8 or something like that, and often work in a small area of that.
I'll post an image sometime. I almost died when it was delivered, and then died some more when hubby unpacked it. LOL. My 21" is upstairs with my painting easel and table so I can take breaks and talk on here. :)
I also use Cintiq 21' in my office but the problem is that the Cintiq monitor is should be connected either CPU or Laptop
but i want to use tablets like i can carry anywhere in my bag .CPU and Laptop cant carry ..the other tablets are coming for official uses only
the Cintiq quality is not in the normal tablets..