Something I published a little over 9 years ago on the NGC Boards. At that time, NGC allowed PCGS coins in their competitive sets. This is no longer the case and that is good.
A little rumination on the allowance of PCGS coins in the NGC registry
I have been a collector for over 40 years but have only recently begun exclusively collecting coins certified by NGC or PCGS. Truth be told, the reason it took so long for me to enter this area was a kind of silly prejudice that I could HOLD my coins while those poor souls with slabbed coins could only gaze at their hermetically sealed beauties from outside it's plastic cell. Silly yes, but that's what I thought.
Now that I am getting older, I have begun planning for my eventual demise and am feeling the need to make my collection as convertible as possible to my heir. Certified coins are the ideal way, at least in the present market, to ensure she has a chance of a fair deal. For that reason, I have liquidated vast amounts of my collection to create my registry sets.
For me, since I have zero chance of ever winning a significant category, the registry sets provide a very convenient way to organize my collection and to provide a rough retail (insurance) market value. Of course, the lure of the chase is also enhanced by seeing my list of coins and planning my upgrades. It doesn't matter to me if the coins are NGC (which I prefer) or PCGS as they are both respected in the numismatic community. I am very thankful that NGC has the confidence to stack its coins against the PCGS coins. I applaud NGC for that and I will always look for an NGC coin first before adding any coins to my collection.