I don't have a Bamboo Tablet (VisTablet PenPad), but I have it on Full Area + osu! fullscreened to 1024x768 (I can only use the entire pad, I ca't force a portion of the tablet area)
I used to use a mouse but I got stiff fingers when using higher sensitivities (higher than 1x @ 800dpi). So I got a bamboo tablet and use the full area which works out much more comfortable, this is the only particular reason lol, nothing to do with skill (which I don't have). I am just too used to moving my hand a lot from other games I play.