>I own the Sigma but would consider selling it if the older >80-400 was optically as good or better. The new versions is >out of reach but nice used 80-400's are less than $1000.00.
I can't answer your question regarding comparison as I've never used the Sigma but I am not and have never been a fan of the original 80-400. The IQ is pretty good but the auto focusing and handling are sub par in my opinion. If you like how your Sigma focuses and handles I say skip the 80-400. Or try to find an 80-400 locally you can rent or test on your camera and decide.
I sold my 80-400 to buy the Sigma 150-500. Reason being the 80-400 was slow to focus, it has no focusing motor in the lens. My version was a bit soft at 400mm. The Sigma focus is faster and has the extra reach at 500mm. It is a larger lens than the 80-400, but I an very happy with it. Have used it with a D300, D700 and D800. I think the new version of the 80-400 is a bit overpriced- just my opinion.
I have the Sigma 50-500mm OS and sold my 80-400mm Nikon to buy it. In short, it's everything the Nikon wasn't for me. It's a bit heavy, but the slick AF and image quality far outweigh any disadvantages.
I'd probably choose the 50-500 OS over the older 80-400. But I expect the new 80-400 will be equal or superior in almost every way. That's on paper right now, but Nikon has a very good reputation for optical quality in upper end lenses.
The challenge is price. If the 80-400 is available used in the $800-900 range, it's a pretty good lens for the money. You're getting good optical quality and VR but sacrificing AF speed. Still, it's probably better than the Tamron 200-500 or Sigma 150-500 alternatives. And both of those lenses are pretty good for consumer lenses.
I agree. Although the extra length is at the wrong end (120mm instead of 80mm), the current Sigma 120-300mm f2.8 OS + a x1.4 TC must be a good bet too. My only worry is that this lens is still a relatively new kid on the block and although I've read some great reviews and seen some outstanding images on the forums, I don't understand why it was replaced so quickly. Can anyone enlighten me please?
The "old" model Sigma 120-300 OS HSM EX lens had a brittle plastic lens hood that was prone to cracking. Also, many of them would not focus properly when the lens was oriented at 45 degrees up or more- a real pain for BIF shooters! And, the tripod foot was pretty sticky-you practically had to force it to vertical. Hopefully, they fixed all that because optically it was and is a champ and the focal range and wide f2.8 aperture are great.
As to the original post-I would opt for the Nikkor 80-400 AF-D and it's f5.6 aperture at the long end over the Sigma's (50-50 and 150-500) dark f6.3. The 80-400 actually focuses decently quick on pro type bodies with strong screw drives like D300's and above.
I have the 150-500, and have borrowed my dad's 80-400 a few times. The first time was before I got the siggy, and (on the D90 I was using at the time) found the 80-400 somewhat painful due to focus speed.
But I've borrowed the 80-400 a couple of times recently (using my current D4, and with ability to compare the lenses directly).
I bring up the camera model because I found the 80-400 focus speed pretty decent with the D4. I was able to get decent BIF shots with it, which surprised me.
But as far as image quality, they seem pretty similar. Certainly, both have given me images with which I've been happy. I'll see if I can post some of them when I get home.
Some other thoughts: the tripod mount on the Sigma is much better (though turn off OS when on tripod). I use RRS' long lens support on the Sigma, and that does help. Oh, and the size difference is appreciable; the Nikkor is much easier to carry/fits in much smaller space in bag.