Nimble body Necessary?

I'm making a sindit and considering between maxing Double Stab or Nimble Body. I have friends telling me that the Acc isn't needed because thiefs already have enough of that and you'll only suffer with that in lower levels and it wont matter at higher levels. Double Stab can be useful at higher levels as a finisher skill that uses less mp.

What do you think is a better choice? http://forums.mapletip.com/index.php?showtopic=114371