The main function of a rest is to hold your arrow in position. Virtually all do this adequately. Some have nice micro adjust features that make it easier to get your arrow into this position. Personally, I haven't found this to be extremely important. Once I get my rest adjusted, I tend to leave it that way. Center shot doesn't change and I make most vertical adjustments at the nock point.

The other funtion of a rest is to secure your arrow, to keep it from falling off. At the same time, it is helpful if it keeps the arrow from making noise. The whisker biscuit excells in these areas. It not only keeps the arrow in place at all times, it cushions it against making any noise when bumping something with the arrow. This can be very important to a hunter.