Okay, thinking about getting (but not committed yet) a 24-70. Question is which one? PhotoZone shows the Nikkor as superior across all focals, but to be honest, I see some excellent images being posted here from the Tamron at about 1/3rd less than the Nikkor. Tammy is a little lighter and a little shorter than the Nikkor, but neither is small. Not sure a 24-70 is even worth it if I have a Sigma ART 50 and 24 (don't have my hands on the Sigma 24 ART yet, but it's a foregone conclusion) and already have the 24-120 which while not great is often good enough ... Thoughts?