They both have a lot of experience at it, and apparently only Rand has gotten better at seing through the other's faints.

Leaving the matter of Egwene aside, Rand did the right thing. It was hopeless to try to convince TV, and if he tried without the nations and his inner circle present, he would still have been arguing a month later. Much better to say for now the one thing related to that meeting that would at least unite the WT for sure, and motivate it to gather all the rulers (but Murandy's it appears - Elaida would be so proud).

At least so far Egwene intends to play it fair and speaks of convincing Rand. Others (Siuan, notably) might have chosen to deceive and it will be interesting to see if it goes that way, when the Aes Sedai realize Rand has no idea the last missing seal (a matter that until it's resolved would make breaking the other seals pointless), the one found by Nynaeve and Elayne, is already broken. No doubt some in the Hall etc. will want to play it that way - we have the missing seal and won't give it to you unless you agree to delay breaking the seals (they can even say that straight out), but with the post TGS Egwene I'm not sure what to expect (I'm leaning toward her finding the risk it backfires too great when Rand finds out, in a "Siuan is better hope Logain never
exposes her lies about the Reds" kind of way). If she chooses deception, I could see Elayne putting her convictions before Rand if Rand's arguments failed to convince her, but I highly doubt Nynaeve would agree to deceive Rand another time after what happened with Tam, maybe even at the price of her allegiance to the WT (I don't think it would come to that, though).

Nynaeve has certainly wisened up a lot, and her discretion is most commendable. The Light knows what Egwene would think of Rand had Nynaeve shared everything about what she went through with him recently.