Sigma 120-400mm OS Vs Nikkor 80-400mm VR?

I have read very few reviews on both these lenses to come to a firm decision. I know the Nikkor is obviously better, but is it worth the price difference? I do birding, but no action or sports photography.

Are there any Nikkor/ Sony compatible lenses?

My husband bought a Sony DSLR and I have a Nikon DSLR. We're trying to invest in lenses that will benefit us both but are finding that Nikkor lenses fall firmly out of our price range. I was wondering if there are any third party lens manufacturers that are compatible for both Sony and Nikon.

Nikkor 55-300vr or the 70-300vr?

Which one is better, I would use it in a DX body.

Is this overall a good lens?

Http://www.nikonusa.com/Find-Your-Nikon/Product/Camera-Lenses/2190/AF-S-DX-Micro-NIKKOR-85mm-f/3.5G-ED-VR.html

I'm guessing all Nikon lenses fit all Nikon cameras also right?

Nikkor 16-85mm 3.5-5.6G VS Sigma 17-70mm f2.8?

Nikkor 16-85mm 3.5-5.6G VS Sigma 17-70mm f2.8?

New 70-200 sigma (nikon) or 80-200 nikkor?

Which is better?
thanks

Added (1). Thank you

@yes I hope to you it as more as possible
and
@the 80-200 hasn't vibration control (and is the only one I tried… It seemed a very good lens)

but which is the better and why? There are alternatives (around this price)?

Thoughts on Nikkor 85mm f1.4?

I'm interested in buying this lens as I own the awesome 50mm f1.4, would you recommend this? Its not for a specific purpose, but I own these following lenses and thought it might complete it: sigma 10-20mm, nikkor 50mm and 70-300mm. Would you say it fits in nicely or should I go for a different lens. Budget is an issue, or else would have bought sigma 150mm macro.

Second hand Nikkor 12-24? Or Tokina 11-16?

I've been wanting a wide angle lens for quite some time now and have the following opportunities to buy them:

Either a brand-new Tokina 11-16, which I have heard is excellent, if not better that the Nikkors. However, I'm afraid that I might get a defective piece (which has happened to a number of people and customer service where I live is not that great). Also, will it work with future cameras the way a 20 year old Nikkor works almost perfectly with today's cameras?

Or a second-hand Nikkor 12-24 f/4. I just got the lense to test out today and so far the pictures have been pretty good. I can get it for about $550. Unfortunately, the outer glass elements are not so clean; the front and rear have dust and minor scratches along with what looks like water droplets, and the grips are pretty used. The person offering it to me is a photographer who must have used the lens alot.

My budget is something under $650.

Is it worth to sell my lens?

I'm using a Nikon full frame body. But at the same time I'm using Tokina 12-24mm f/4. The thing is. The lens is to wide until there will be a fisheye effect if I put the zoom at '12mm'.Is it worth to sell it and buy Tamron 17-50mm f/2.8 & Nikkor 50mm f/1.8?

How good is Sigma's 70-200mm F2.8 EX DG APOMacro HSM IIlens?

I'm wondering why is it half the price of nikkor's lense! Is it because Sigma hides a very big BAD secret?