I think there are a few reasons you see PCGS coins selling for multiples of similar coins in NGC holders.

To keep this post to a reasonable length, I'll stick to only the most obvious and important one.

I?ve posed the question to maybe a couple of dozen dealers over the past few years. Some said they think PCGS grades a little tougher (especially on very high-end modern material), some think there?s no difference between NGC and PCGS, and I?ve yet to hear a dealer say NGC is tougher. My personal experience is likewise that PCGS is tougher on the modern stuff and some random specialties like California Fractional Gold, but on most pre-war coinage NGC and PCGS seem about the same. I think that?s more or less borne out by auction trends.

This doesn?t mean PCGS is better. In fact, for reasons unrelated to the grading standards, I use NGC a lot more than I do PCGS. Aside from being faster and cheaper, NGC gets my vote if only for sparing me the annoyance of looking up those stupid PCGS coin numbers. Anyway, the point is that protecting the value of our coins depends on consistency, not toughness. So long as a service grades consistently enough to be predictable, the marketplace should value the coins accordingly. I think NGC and PCGS both satisfy that test more than adequately.