Audio Supports

The reason that three is better than four is that three points define a plane. This means that it's virtually impossible to have four points equally support something. This is why a stool with three legs won't rock but ones with four almost always do. If the legs can be adjusted then I'm sure that it's possible to set things up such that it really doesn't make a difference.

Nordost recommends putting three sort kones in specified locations under equipment and then moving the 4th around looking for the "low" point.

4 of a kind beats 3 of a kind,as Buconero says.

Mceljo is correct in theory, but I find 4 easier to level.

In my experiments 3 always sounds substantially better than 4, more grounded. Unless you go round with a stethscope and dial in the spikes precisely then 4 is less stable. It always amazes me when designers claim they make the ultimate product, cost no object, and put 4 feet on their gear shows they dont listen.