Which is the best dither? Truthfully I have no idea. There are several different types available. Before we tackle which is the best dither, let’s examine what dithering does.
In short dither is used during bit reduction i.e. 24bit to 16bit. What it essentially does is add noise shaping to smooth out the reduction. It is something that you use only once and it is placed at the very end when you are converting the bit rate. Because it causes degradation, do not use it more than once. That is dithering in a nutshell. For a more in depth description of what dither is and isn’t check out this Article by Bob Katz Explaining Dither.
There are several different types of dither algorithms that I always hear being mentioned when people talk about it. The most commons are POW-R, UV22 (Apogee), MBit + (Izotope), and the Waves dither found in the L2 limiters. I have used all but the Mbit +. I personally don’t have a preference. I try to use the one I feel is the best available in the program I’m using. If i’m using Cubase I use the UV22hr, if I am using Logic or ProTools I use the POW-R. You have probably heard a recording that has used eachone of these dither algorithms, except you just don’t know which one.
If you really want to know which is the best, don’t depend on me to tell you. What you should do is two things. First research the different dithers and how they work. Second try a blind dither test. I have done both of those. In the blind test I found that I prefered the Waves L2 dither.