Part of the problem in understanding both grades and conditions as a guide to coin value is one of definition.
Condition was what was used many years ago to give a very exact detailed description of a coins state of preservation. As an example, today if I were giving this 1951-S Washington Carver commemorative half dollar a condition, I would say: Full brilliant luster, no hint of toning, average strike on reverse, especially strong strike on obverse, particularly at the center. Smallest of abrasions seen on the reverse lower left field which is really the only area of distraction caused by hits or bag marks.
Condition description was almost a necessity in years gone by to describe the details about a coin, since photographs were often impossible, except in the cases of auction catalogs. It was not so long ago that a fair amount of trade was achieved via the old fashioned price list and in many cases the seller wanted to be sure to give the best possible description. Thus condition was listed, rather than just a GRADE.
This coin is in an NGC holder, which lists it's GRADE as MS-66.
GRADE is nothing more than the shorthand equivalent of what the condition of a coin may be. Rather than taking all the time to give exact descriptions of strike, rim preservation, luster, toning, bag marks, hit marks, railroad tracks, cleaned, dipped, tooled and a whole host of other specific examinations of a coin, the GRADE summarizes all of that.
Today most coins are presented with photographs. Although photos may sometimes be of little help, or even misleading, the fact that photos can often be seen today is yet another reason why condition is listed less and a more concise GRADE replaces condition.
When I started collecting, no one I knew listed a numeric grade for a coin. You had Good, Fine, Very Fine, and Uncirculated as the major "grades". As the value of coins increased, especially in the beginning of the 1970's, and coins became a potential INVESTMENT rather than just a hobby, the Grades became more exact and included an ever widening selection to include Nearly Fine, Fine+, Almost Very Fine, Almost Uncirculated, Brilliant Uncirculated, and on and on and on. In some cases, I'm sure that sellers made up the terms they used, rather than sticking to a strict list of nomenclature for those grades.
The next step was the popularity of numeric grades, which is what most everyone uses now. We no longer even have to call a coin a Very Fine, we just call it a 25.
When ANACS switched over from certifying coins as genuine to also offering their opinion on grade, and as a number of other companies jumped on that band wagon in the late 1980's, the exactitude of grading was blown to the wind.
Anyone that lived through those late 1980's third party grading (and when I say party, they were really having a party) knows that NONE of the dozen different companies that tried their luck to gain a market share were always remotely close to their own grading from month to month, let alone year to year.
That includes the two remaining contenders, NGC and PCGS. There are still those out there who claim they can take early examples of grading from those companies, resubmit them, and gain a point or two. That might be true for the .0001% of collectors who achieve a level of grading SKILL that few ever actually attain.
The vast (and I mean really seriously VAST) percentage of previously submitted coins that might make another point or two have already been found. Old time collections might come on the market and offer a few more from time to time, but there are not those huge numbers that we saw in the mid 1990's.
Now you need to stop and step back from the fact that you are a coin collector. Just consider yourself only a collector for a moment.
THIS EXACT same sequence occurs for EVERY collectible as it ramps up toward an investment possibility.
It is ALWAYS the same. First conditions, then loose grades, then complicated grades, then numerical grades, then third party grading, then changes and adjustments to third party grading.
The bottom line to all of it is pretty simple. Either you believe in third party grading, or you don't. It's a bit like politics or religion. People can yelp and scream and give wonderful reasons for or against.
But you are voting with your money. Maybe your money isn't important (I've heard it said), maybe you have no relatives that you want your collection to go to, maybe you are only in it for the joy of collecting (which in no way reduces the possible amount that you might spend).
So in the end, it does come down to the vote. Your money is your ballot.