Currently there is no drawback to choosing the Nike+ versions. You get everything the non-Nike+ watch has, plus additional faces and the choice of Nike+ exclusive bands.
Used to be the Nike+ models launched a couple weeks later than the regular ones so you had to wait. That changed this year.
The only disadvantage of buying a Nike AW, is you can only order it with a Nike band/loop. Which, if you want the Nike band/loop anyway, is then a no-brainer.