I've been using a graphire A6 at home, and Intuos A5 at work, and have just ordered a new Intuos A5 for home.
There's a big difference in feel between the graphire and Intuos I think, and better sensitivity levels too, but if this is your first tablet, you probably won't notice any difference (regarding the sensitivity I mean) ... on the size front, A5 is ideal for me... the whole tablet takes up about the same amount of space as a horizontal sheet of A4 paper, If I had an A4 tablet, I'd need a bigger desk... the drawing feeling is good on A5 btw, and no its not like drawing on a piece of A5 paper, the dimensions are mapped out the size of your monitor nicely.
A5 = great size
Intuos = better technology.
your choice I guess - simplejack
"Learn as much as I can at whatever cost, then give it away for free and ask for nothing in return" - (me!)