I've been using different wacoms simultaneously. I have a large active area (intuos 4, comparable to intuos pro) at the office while I'm using a small active area (bamboo, comparable with intuos) at home. I upgraded to Intuos pen and touch medium at home now and I'm very satisfied with it.

Intuos pro's pressure sensitivity, touch ring and precision mode could be also be worth taking into consideration (I don't use it though).  I'm now working on the same painting on the intuos 4 and intuos medium and I started to finally notice the hardly noticeable difference between the pen pressure though the pro has double sensitivity on paper. 

Personally, having been able to work with different Wacoms, Intuos medium is just what I need. Another thing I get from the intuos medium is that it fits my table just right. I work with my wacom directly on the side of my keyboard so it takes a lot of space. Had I chose the pro, either my keyboard or tablet would pop out of the table which isn't good for stability. 

Final thoughts on my recommendation: if your painting style doesn't have to rely on highly sensitive pen pressure and pen tilt, if you won't be using precision mode (which is useful when detailing your painting while zoomed out... i don't don't do that though), if you don't press on wacom keys that much, if your display is  23" or higher. then the intuos pen and touch medium would be the best bang for buck for you.