Well I can say the Nikkor is $260 new (grey) vs. nearly $400 for the Sigma. Also I would hold off buying any Sigma HSM lenses for a couple of months until supplies of those that have problems with the D200 deplete.
i have the sigma on my d200. its great apart from shooting an over exposed white envlope on a dark desk at f1.4... i get ca accross the picture if i crop right in, easly fixable in photo shop. if it's for shooting low light stuff (at night, in the shadows) at less then a third of the nikkor price, stuff f2.8, get it.
I have no experience with either but think that the generalities still apply where you save big bucks with sigma and mostly get 90 percent of the performance with the better glass but you take a bit of a chance two ways. They seem to have sample variations that are pretty big from one sample to another. You are taking a bit of a gamble then. Then there is the compatibility. It's rarely a problem until the next generation of bodies but there are then often compatibility issues. Sigma is great a fixing those but of course that means being without for a while while it gets re-chipped and then there are limits. Sigma doesn't do some of the older lenses eventually. So you can save and if you are fortunate you get a great copy at a great price. Some headaches in the future are to be expected on the other hand - and most of the lenses even though very good just aren't quite is the same league as the genuine deal.
The case here you also give up use on a Film body or future FF if Nikon goes that route.
Tough choice!
What's the difference between the sigma 30/1.4 and nikon 28/2.8? 2mm and Two stops to be exact. I'm not trying to be a smart @ss, that's really the difference.
I originally compared the sigma 30/1.4 and nikon 28.14 - I am a wedding shooter and sometimes a 1.4 aperature is the difference for me getting/not getting the shot in a low light situation without flash (some churches do not permit flash). I also love selective/shallow DOF. The nikon 28/1.4 is wonderful but I would have had to second mortgage the house for it. The sigma was reasonably priced (for me).
I got an excellent sigma sample. Sharp, even wide open. But given the sample variation, you are best to try one out in person.
If you need shallow DOF or low light capability, the sigma is great value. If that is of no concern to you, get the Nikkor 28/2.8
