A raised rest will be slightly more accurate, as far as busting X-rings when target shooting anyway. Raised rests can break, especially in cold weather (just ask a friend of mine about that one<img src=icon_smile_wink.gif border=0 align=middle>). An arrow can fall off a raised rest and raised rests can be noisy.

In a hunting situation, off the shelf is more convenient, quieter, quicker into action and plenty accurate to put an arrow where it needs to be.