I'm about to purchase a zoom lens for my D600 and I'm down to the Nikon 24-120 vs the Sigma 24-105. Based on what I've read on the internet (I'm no pro so may have misunderstood some of the info) and my own preferences, the score card at the moment looks like this: Nikon pros - longer range - weather sealed (it's cold and wet where I live) - lighter Sigma pros - from what I can work out, this lens has the edge on sharpness and general IQ (?), but it's a bit hard for me to assess how much this translates into actual difference for my needs. I'm an amateur and for the most part I shoot landscapes, architecture, macros and abstracts. I want to venture more into street photography and portraits, eventually. The price turns out equal for me. While the Nikon costs more where I live, I have lots of filters in that size, but would need to purchase 82mm filters for the Sigma (and they're expensive). This zoom, along with my 50mm prime, will serve as my main lenses for a good while. So, if anyone has experiences with one or both lenses, or have been through the same decision process, please let me know your two cents. Thanks!