quality depends on more than the zoom capability.. the optics (number of elements in the lens and precision), and AF features of the lens determine quality really. Generally speaking, the cheaper the lens, the more you won't like it. What you are paying for mostly in a 24-70mm 2.4 is the fast f/2.4 aperature, which will get you more depth of field and better under low-light conditions. Cheaper lenses are typically around f/4.5 or so, which can limit your options. General rule of thumb: spend a good amount of money on your body, and as much as you can on your lens
