Your questions are answered in the monk guide thread if you browse through the last several pages.
Short version: on paper, Vere is about 10% more damage than Oatixur. Spharai is about 5% more damage than Oatixur. The new delve weapon is about 1-2% behind Spharai.
My experience: I have 119 Vere. I have a LS mate with 119 Spharai. Other monks in the LS have Oatixur. Theoretically I should be top on the parse, but it's not always the case. There are times when I don't top the parse due to the variety of factors that play a much bigger difference than my weapon; IE - buffs wearing, debuffs being applied/removed, getting stunned, being accuracy capped....
The defensive help from Spharai is based on the relevance of countering. Some bosses have aoe or conal attacks which you cannot counter. Oatixur has PDT on it, which will actually make it a better defensive weapon than anything else in most event situations.
If you want something to separate you from bandwagon monks, then I honestly think the biggest factor is what weapon you think looks the coolest or will make you the most proud. You're not going to see much of a difference either way.