The problem is that "all the rest" comprises a wide diversity of companies and guarantees, as well as many different motives for doing the coin grading. For example, there is a whole category of major dealers who do their own slabbing. These dealers grade more or less consistently, guarantee that the coins are genuine, and offer some kind of (usually short term) guarantee. Contrast this type of slabber with someone like SGS (Star Grading Service,) which is widely reviled as the worst of the worst. SGS only issues 11 grades, MS-60 through MS-70, no matter how bad the coin is! A coin that was sent to them as a test coin came back (graded PR-70) with a big fingerprint added to it! SGS is frequently cited as the culprit when complaints about graded coin value fraud come in. Is it really fair to rank SGS "equally" with, say, PCI, which has been around for awhile but just doesn't grade as consistently as others?
I have created a proposal for a five tier ranking system for grading services in an attempt to remedy these inconsistencies. The first and second tier are unchanged. The third tier carries some of the "better" of the rest of the companies. The fourth tier is for self-slabbing dealers who meet certain conditions regarding buyer recourse and guarantees. And the fifth tier is called the "bottom tier," so that we can finally put grading disservices like SGS in their place!