Depends on how much you use. Beaver silencers can vary in weight--some are wider, some are longer, fur can be longer or shorter, thicker or thinner,the hide thickness varies, etc. Probably not a huge difference, but the difference in the weight of silencer materials in general isn't normally huge.
My personal favorite is "cat whiskers". Properly applied and tuned, I haven't found anything that works better. Most folks I've seen don't apply them properly, and they use way too much and/or cut them way too long.
First, tie them on around the string. This way you can move them up or down the string for tuning. I've seen bows where moving the silencers an inch or so made a HUGE difference.
Second, more isn't better, especially if they are too long. Long cat whiskers will make their own slapping noise. I like them fairly thick but short. I'll fold a 6" piece in half (or combine two 3" pieces if I want two colors), tie them on around the string, and trim them back. I'll usually trim one piece shorter than the other--looks good, although I'm not sure that it works any better. An inch to 1.5" is the max length, and in some cases I cut them a good bit shorter.
I love the looks of fur, but tuning is a pain in the butt, and I like to use a small amount of silencer on my string. I also prefer a material that doesn't hold water, burrs, or scent.
It doesn't hurt that they are cheap also. The only drawback I know of is you may want an extra set of hands available, at least until you get the hang of tying them on.