Having done business with both WF and BN, I now strongly prefer WF. And as the owner of a RB signature ideal cut purchased before I knew about the ACA's, I believe the ACA's have much tighter criteria for super ideal cut stones so I'd go with an ACA. Just my 2 cents.
ETA: Don't forget to consider upgrade policy, or lack thereof if you go with BN...
Ditto. You also get more information about the ACA before your purchase, including a magnified pic of the stone and the idealscope image. BN has no upgrade policy, either, which is an issue for me. Prices are comparable, probably actually cheaper with WF, depending on what you''re looking for. I like that most of the ACAs are AGS graded, too.
I, too, have purchased from both WF and BN...and honestly, both transactions were fine. WF definitely provides more detailed info upfront (including their wonderful, magnified pictures). All ACAs are in-house, so you can have people look at the particular stone in question and answer all your questions. I do believe that BN''s signature ideals are also in-house, so you could probably get detailed info as well from someone who can eyeball the stone for you, but I just don''t know that you would be able to speak to that person directly.
WF has a lifetime upgrade policy if that interests you, along with a 10-day return. BN''s return period is 30 days.