A Bamboo will work just fine. I've had mine for three years, and when it'll die down I'll get another Bamboo. I don't really what would make an Intuos that much greater other than the price. And Bamboo have improved since mine, now with 1024 pressure levels (mine only had 512) I don't think you'll see the difference going up to 2048 for the Intuos.
And for the size, well, I'm used to draw on a small scale with my tablet, even though I draw on 14'' by 11'' paper. You get used to it, it'd be weird the first times though XD
hey i can help i been drawing with my bamboo for six years and no i never upgraded to a intuous. if you can save the money do its not that much of a difference besides what you said. i mean year pressure sensitivity is nice if you are lazy and dont want to change the pen darkness in the pen options program. and whatnot but my art comes along just fine with a simple bamboo, especially if its for tattoos and not really really big art. yes it works excellent for photoshop but let me tell you a few other programs to look at that i use besides photoshop. For drawing i personally am in love with the sketchbook pro series they really took alot of time to make the stylus feel like a real pencil and the flowidity of the pen on the screen is more fluid then when drawing on photoshop. Here i can show you [link] now im saying you cant draw in photoshop but i personally use it for coloring not drawing.