Blue Nile Astor Princess Diamond - GemEx Certificate Useful or Not?

First of all I’d like to thank you for your knowledge & advice that you put into your website. So, basically I have narrowed down my choices between these two stones: Blue Nile Astor Princess diamond and Whiteflash A Cut Above Princess diamond. Which in your opinion is the better princess cut diamond?

This Astor TM diamond, 0.5 carat I color vvs2 clarity has ideal proportions and a diamond grading report from GIA

0.50 Carat I-VVS2 AstorPrincess Cut Diamond

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This Astor TM diamond, 0.7 carat G color vvs2 clarity has ideal proportions and a diamond grading report from GIA

0.70 Carat G-VVS2 AstorPrincess Cut Diamond

Diamond Certification: All About GIA Diamonds

This Astor TM diamond, 0.25 carat E color vs2 clarity has ideal proportions and a diamond grading report from GIA

0.25 Carat E-VS2 AstorPrincess Cut Diamond

This Astor TM diamond, 0.43 carat I color vvs1 clarity has ideal proportions and a diamond grading report from GIA

0.43 Carat I-VVS1 AstorPrincess Cut Diamond

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This Astor TM diamond, 1.2 carat H color vs2 clarity has ideal proportions and a diamond grading report from GIA

1.20 Carat H-VS2 AstorPrincess Cut Diamond