My question is, Sigma 10-20 or Tokina 12-24? I would love the Nikon 12-24 but just can't justify the price difference (little one on the way so gotta watch the pennies where I can). My main use for the lens is probably going to be the urban thing (i.e, buildings, occasional people, anything architectually interesting). The wider end of the Sigma might be nice, but I'm more interested in making sure I get a quality piece of glass. I'd love to hear from anyone who has used one or both and know what your thoughts are. Thanks.