Another thing she might prefer about the istD is its size. The 300D is more chunky than the istD and the grip sticks out more. There are other differences, like the location of the LCD, the way the controls are arranged, that sort of thing.
> I would think that looking through the viewfinders of both > would convice someone > completely. The problem is usually the store does not have > both in stock. So go > with her, let her check out the Canon, and yours.

