GIA Clarity Grading

I had two consultations (today and yesterday) where both stones were GIA certified VS2 and they were were like night and day. 

When clients comes in to my office for an appraisal/consultation I look at the stone while they hold onto the GIA certificate. I tell them what I see which usually matches the GIA certificate. To me: the first stone was VVS2 and the second was SI1.

I had no problems telling the clients with the perceived VVS2 (even if it is VS1) stone that I thought they had a really good diamond and they walked away very happy. Wth regard to the other stone, although VS2 & SI1 are only one grade apart, on a 4.01ct PS D it's a 33% difference on Rapaport. I told them to keep looking....other considerations was that the black crystal could seen through the table was reflecting, the symmmetry was graded only as good (is there a lower classification?, I have not seen one) it was lopsided, it had a thick to very thick girdle and at .01ct over 4ct it had obviously been pushed from 3.00 - 3.99ct stone (althougth the reflecting black crystal would have still been there).

The point is that I think apart from all the other nuances of diamond appraising, clarity is still the hardest to standardize.
With clarity, you have to spend more time to inspect the stone under magnification from different angles.

Pricescope's research on cert's last year still holds for me. GIA may be the overall authority but their clarity calling is not 100%. On the other hand EGL, to me, is better on clarity (Vote 1: SI3)