There are definitely limitations to digital drawing tablets, such as being able to zoom in/out instantly with your own eyes. This alone is really frustrating for me when using a tablet to draw, because on paper at a glance you can see if your stuff is in proportion. This allows for a lot more free-flow linework, in my opinion. Unless you own a gigantic tablet or drawing monitor like the Cintiq I guess, you have to manually click to zoom in/out and that disconnects you from where you were, and you have to constantly recalibrate your point of reference - essentially starting over every time you click the zoom button.
Not sure if that made any sense but to me it's a real limitation of the current drawing technology. Of course you can get used to it and work around it or even probably turn it into a benefit but I’m not there yet and that was a strength of mine when working on traditional paper. I’m finding that digital works best for really perfect work, or concentrating on one area. Whole body is either super reduced gestural with minimal detail (because you’re never zooming in), or you have to attack each body area sequentially by zooming in/out over and over and it drives me crazy.
So, if I were to draw from live model, I would still choose paper over digital. Incidentally, I stopped by an Apple store and tested the new ipad pro, and the pencil is just phenomenal with excellent weight. The ipad itself, not so much, most probably due to the paint program which was way inferior to Photoshop. There was barely any noticeable lag to the strokes, but you could still feel the stylus drivers algorithms were over-tweaking your stroke somehow. If I had the money, I would probably go for a Cintiq or maybe the Surface Pro, but the hot keys on the Cintiq are a major bonus.
Just a rant because I’m not happy with my sketches today.