This one! It is Pen and Touch, but I have honestly never bothered with the touch feature and I don´t really feel like it´s needed :P
Active area is indeed the size you can draw on. That section on the Wacom site has an error. It looks like you selected medium, but it's still giving you dimensions for the small. 6 x 3.7 inches is the dimension of the active area for the intuos art/comic/photo small.
Your Wacom Graphire Bluetooth Dimensions: 11.5 x 10.5, Active area: 6 x 8 inches
Small Wacom Intuos Art/Comic/Photo (All the same tablet, different bundled stuff)
Dimensions: 8.25 x 6.7,
Active area: 6 x 3.7
Medium Wacom Intuos Art/Comic/Photo Dimensions: 10.75 x 8.75, Active area: 8.5 x 5.3
The old tablets were the Bamboo and Intuos. The former being the hobbyist tablets, and the Intuos 2, 3, 4, 5 aimed at the professional market. But they changed the name a few years back. The Bamboo became the Intuos series, and the Intuos series became the Intuos Pro series.
Now they've released a new set of tablets, but they didn't add numbers to them, so look out for anything labelled (OLD MODEL) on Amazon, unless you specifically want the previous release.
Confusing huh? :)
tl;dr The Intuos Art Medium has an active area of 8.5 x 5.3. Wacom's site is wrong.
Edit - good formatting is hard here, sorry about the mess.
Right. Your Intuos Art Medium is their hoobyist level product.
The main difference between the Intuos and the Intuos Pro is the pressure levels.
Your current model has 512 pressure levels, as did my old Bamboo. I could certainly tell the difference between 512 and 2048, but I can't comment on the 8192, because I have the previous Intuos Pro model (#2 in the list above). Going by the reviews though, the just released one has some issues.
Intuos pro also has 8 programmable buttons, plus 4 switchable modes for wheel-less rotation pad. I use the keys fairly often, and the rotation thumb pad is nice to have for canvas rotation. I've never used an Intuos Art, but it looks like these are missing.
If I had the choice, I'd buy the same thing again, and in Medium. My bamboo was small and it was just frustrating on a 27" screen.
There is one other alternative, there are a fair few tablets with screens in them now, some of them around the price of the Intuos Pro medium. Maybe that'd be more to your liking. I can't comment though, because I don't have one.
I was looking at this one https://www.amazon.com/Wacom-digital-graphics-drawing-painting/dp/B010LHRVOY I'm not sure if I could bare something smaller than my sketch pad.