And the smaller tablet is actually better for photo editing. It's hard to explain in text why this is the case, but... The larger the tablet the more you have to move the stylus around because the tablet surface, no matter how small, still equates to the full size of your monitor. So a larger tablet means more work. Or rather, a smaller tablet, really makes things easier. I don't know if that makes any sense but once you start using a tablet I think you'll see what I mean. Trust me on this... Get the small or medium sized tablet for photo editing.
Horoscope Fish is right in that the smaller area to work on is actually easier. I put this down to the fact you're moving your entire arm/hand less and this gives you more control. Certainly as a lefty as I rest my entire hand on the tablet itself (not sure if right handers do this?). But there is an option in the software to make the area smaller. So even though the tablet surface is something like 10inchx4inch, my working area is set to about 40% of that measurement.
Unlike a mouse, you cannot lift it up and re-position the cursor, the pad itself is an overlay of the actual screen.
This isn't 100% correct, what Dave_W is describing here is the default setting in the software. There should be an option in your preferences to make it work exactly like a mouse does, so if you are scrolling left to right, and run out of space on your tablet, you can lift the pen and move to the start at the left, and continue where you left off. But this does require you changing the settings in preference.
Personally I would recommend leaving it as default, it becomes more natural after a few days of usage, and if you do often find yourself running out space, turn up the sensitivity. I recommend doing this ever so slightly each day so it doesn't become a massive change all in one go where you'll just get frustrated as the mouse on screen rushes about.
One thing I forgot to mention about the touch is that people who are left handed, like myself, end up turning the touch function off. I, like many other lefties, have that dreaded lefty hook and I smear everything I write with the side of my hand. Unfortunately, that part of my hand causes lots of trouble when using the tablet. But that's not a big deal since I can easily turn it on and off but it's something to think about if you're a lefty and you have the hook.
So very true. I've actually now bound a button on my tablet (pro version) to switching on/off touch so if I alt+tab to another window like my browser I can quickly turn on touch and scroll easily. Useful considering I normally throw the mouse to one side and have the keyboard under my right hand while using the pen in my left hand (great for photoshop for using the hotkeys like spacebar)
I don't think there is a major difference between the pro and non-pro version, I'm sure they use the exact same drivers/software to run as well. On the pro version you get some buttons on the side which are nice to have, but not required considering they are normally just mappings to keyboard hotkeys for your major software. I think the pro version might have more pressure sensitivities/layers, so it's something like non-pro = 1024 levels of pressure is supported, pro version has double that maybe. 1024 is already more than most of us will ever use. oh and pro has wireless out of the box, again it's a nice to have but not required.
So, Don't forget to visit the mapping option on the grip pen in the drivers, and set the tablet area to 'Portion'. While there switch 'Mode' to either Mouse or leave it as default Pen (if you are lefty, set the orientation here of your express keys to right). Also go to the Pen tab and customise your 'Tip Fill'. I'd also recommend changing the pen nib to one that feels better on the tablet surface. I use the white end nib myself as it has a sort of softness to it that I like, rather than a scratching feeling.
If you really want to get into having some fun in photoshop for example. check out Phlearn.com (when they fix the database). Aaron who runs the company does all his work using a wacom tablet. I've seen some graphic designers at my wifes work who don't even bother to pick up a mouse anymore, they just do everything with the pen now.