Grading is far more objective than subjective. For example, any moderately experienced collector can grade a generic VF or generic EF Lincoln. There are three key areas where subjectivity come into play: close numerical grades, die state and strike adjustments, and difficult series to grade.
When I started collecting - back when dinosaurs roamed - the standard grade splits were AG/G/VG/F/VF/EF/AU/UNC/BU/Gem BU. Grading was done by Brown & Dunn, and later Photograde. Increasing numbers of deceptive counterfeits, greater demand for numerical grades, and the rise of sight-unseen sales led to TPGs, but also are now leading to much greater consistency in grading.
Some of the most difficult grading calls are the extremely close numerical grades. G-4/G-6, F-12/F-15, AU-53/AU-55, and MS-64/65 can be tough. Expect some variance with these close calls.
Grade adjustments for die wear and strike quality are vital in some series. These adjustments happen regularly for the series with wide variations in strike, such as Buffalos and Morgans. Eye appeal adjustments also exist, mainly for MS-60 and up coins, and in lower grade coins exhibiting significant (but market-acceptable) surface disruption.
The difficult to grade series will have greater grading variation. That's natural. Lincolns, Barber coinaqe, etc. are comparatively easier to grade than Buffalos and coins that rarely circulated, such as classic commemoratives.
Each
TPG has strengths and weaknesses. PCGS Morgans trade higher than NGC Morgans, reflecting a market adjustment for grading differential. Canadian grading standards are sharply different than U.S. grading standards, and ICCS is much more consistent for Canadian coins than PCGS. ANACS does better with die variety attribution. All of the major TPGs do well with authentication.
The key, however, is being able to grade your own coins. Several people have already said this upthread, but always buy the coin and not the slab. A coin in an
authentic major TPG slab says two things: (1) the coin is genuine and backed by a guarantee and (2) an expert has been paid for an informed opinion as to grade. Those are valuable commodities, and well worth the price. Just one example should illustrate my point. Given the abundance of good counterfeits floating around, which would you rather buy for $1350 or so as bullion: a raw 1907 $20 Liberty or a slabbed genuine details 1907 $20 Liberty for $15-20 more?
CCF is a priceless resource for grading. When you hit a coin that leaves you in doubt, post it. If you have a coin that is on the bubble of being worth submitting to a
TPG, submit the photos online here first. People will weigh in on authenticity and grade and variety. The CCF submission fee can't be beat, but be prepared for honest opinions. On the other hand, those opinions come from a herd people with collective centuries of experience.
Just my
Two Cents from the curmudgeon's corner.