Sony E-Mount 10-18 f4 or Tokina 11-16 f2.8

One more option to consider:

If you don't mind the cost, you might want to consider getting the Metabones Speed Booster, and get a Canon copy of the Tokina lens.  You end up with a true full frame 11-16mm f2 from the stop increase.  I have the 10-18, and really love it - the stabilization is great and I use this for a lot of photo and video work as well.  I use my Voigt 15mm for serious landscape work, but the 10-18 is very close.

And now as I type this, it would be pretty amazing to have an f2.0 full frame 11-16mm on my Nex.  Was waiting for the FD version of the Speed Booster but might just get the current EF...

--
http://www.500px.com/kazkang