I've always wondered about this. If one is putting together a set, does it benefit them to wait and plug them in PCGS all at once or does putting them in as you get them give the same result. Does putting your set in when it's "complete" offer a better ranking than if you do it one at a time as you get them?
Tom has answered your question regarding points, but I will add there is great benefit to putting them in as you get them, as the registry becomes yours inventory report, want list, gallery, and motivation to finish the set. People can watch your progress as the set grows, and you can enjoy moving up the ranks with each new piece. Just some thoughts...
If a person starts a PCGS or NGC registry set do all of the coins in the grading service the set is registered in have to be only coins graded by that service? I would think so but, what if the set of coins a person is assembling has coins from both grading services.
You can have sets with coins graded from multiple TPG's. I am putting together a set that has both NGC and PCGS in it.
Same ranking, only advantage of waiting is all your coins end up in matching holders instead of a mish-match of styles.
NGC accepts PCGS coins in their registry sets. I believe, but not sure, that they do give registry points for PCGS slabbed coins in their sets. PCGS only gives registry set points for their slabs, but you can put in NGC, ANACS and any slabbed or raw coins. You just don't get registry points.
I created a showcase set at PCGS since 23 of the 29 coins in my Liberty Seated type set are in PCGS holders. Eventually I will be acquiring a PCGS example for each of the NGC slabbed coins for uploading to the registry but will retain the NGC coins in my collection and whichever is the nicer of the two would be the one I would put out for display. http://www.pcgs.com/setregistry/showcase.aspx?sc=1877 I really don't care about registry points or rankings it's just an easy way to display my set on the web.