depends on the glass maker; also, there are many different percolators, but some things to consider for all percolators is the size of the slits in the glass (the slits which do the diffusion, the number of slits, and the proportionality in the intake and outtake of the smoke being forced through the percolator (meaning length of the percolator and the different sections of it). Some people claim shower head, some say matrix, some say gridded stem line, the newer one is the pillar perch (which I have yet to try). Personally, My SYN triple nested shower head straight tube has diffused better than any other percolator I've ever tried. love it!
depends on your personal preference. for those who want more chug/less diffusion maybe a dome perc or a tree perc will do, but those who like airy heavily diffused hits something gridded or maybe a matrix perc will do. for those who like flavor a pillar perc or something with less diffusion is better. All depends what your going for, but to answer your question i think there is a best perc for every preference. that just means there are a lot of "best" percs