Ugh, sorry, my head has a hard time not thinking in the immediate new and awesome gadget. Dear god...I went back and read that post, I should not reply to threads before coffee.
I agree with Snarky. I paid $100 for a wacom tablet (3x3 I think (I guess about an A7?)) years ago and pretty much never use it. But, I don't regret it at all. When I do use it, it is nice, but not my thing to use all of the time. Heck, I even mailed it to Darth Mandarb and he used it for a few months and sent it back

Since you do draw a lot, I recommend trying one out, you might not like the feel. If you can't test one, just be prepared to deal with adapting to using it (I think this is where that "it depends" thing comes in a lot). On mine the surface was really slick so I used to lay a piece of paper over it, felt more natural to me that way.
Regarding size, I recommend against getting one too small. If you want to be a serious artist you will want to save up some money and dump a decent amount on it. This will, after all, become your primary drawing tool. Then again, maybe start small and upgrade later. I feel that my small wacom has kept me from using it more than anything else. Everything feels cramped. Are your options really A4 or A5, that seems off. In the US we tend to have A7 and A4 and then maybe an A3. I would recommend you go for the A4 if you can, that is the size of a piece of notebook paper, which most people are comfortable with drawing on that size surface I think.
Wacom seems to be the defacto standard. I imagine there are other brands out there that are better, but I think Wacom just has a better reputation. Just do your research in this regard. Figure out the size problems and if you want to get one at all before worrying about the brand.
Oh, and back to my original screwed up post: Have you considered that route? The non drawing tablet-tablet? One of my problems with the drawing tablet was not seeing the results on the pad with the pen, it didn't sit right in my brain. My wife is an artist and she HATES the wacom tablet (then again she mostly paints and dislikes anything digital). The pricing point on those two is about to get really close I think.
Sorry about my bashing around in your thread.

later,
-junc