You asked
Nikon af s 70 200mm f 2 8g ed vr ii vs sigma 70 200mm f 2 8?
The Nikon is the one I can vouch for here. It's stabilised, autofocuses, and fits full-frame bodies like the D750 and D850, as well as APS-C ones like the D7500. You can see the full list on its page.
I don't have a Sigma page for that lens on the site yet, so I can't compare its specs or price with confidence. Sigma makes good lenses for many mounts, often for much less than the maker's own, but check that your body supports its autofocus features and that Nikon allows third-party lenses on your mount. More on that in third-party lenses.
If you're shooting portraits, a 70-200mm f/2.8 gives you tight headshots and strong background blur from a distance; see the portrait lenses. For landscapes, the lens guide suggests an f/4 zoom is often the smarter buy.
Written by Claude from this site's pages.