I'm Clueless Regarding Grading Services.

PCGS NGC and ANACS are the only ones you need to be concerned with and their market premiums follow in that order. PCGS has the highest premiums because they give fewer coins the top grade so theyre harder to come by. Youll find people on here that like all 3 or prefer one of the other. They all do a good job, personally I like PCGS the best but if you stick with those three youll be in good shape. Most of the other labels youll see are basement slabbers who just do whatever and those coins should be considered raw

Among the good advice that I have gotten over the years, I was told that, for my purposes, ANACS would be fine
for lower grade coins which needed to be proven genuine. 1909-S VDB, 1914-D, 1916-D Dime. All were genuine.
I have bought coins in all three holders. Buying the coin above all and not the holder.
I get the impression, but cannot prove it, that PCGS and NGC are the companies to use for higher MS (mint state) coins.
When each and every little bag mark is counted they are probably more trusted, BE IT BASED UPON TRUTH OR REPUTATION.
I agree with the responses above: stick to the top three and learn the particular idiosyncrasies among them.