For those of you who have tried both, do you find this accurate? The resolution tests on Photography Life show that the 300+1.4TC is actually a bit sharper than the 200-500 at 500mm. Now I know it's 420mm vs 500mm, so not exactly apples to apples, but this is how I'd be using the lens most of the time.
I rented the PF a while back, and when compared, I thought the 200-500 looked sharper in some cases, but now that I look back at those images, I think the focus points might have been slightly different.
Why compare one lens at 420mm and the other at 500? Should have measurement of 200-500 at 420mm to be a valid comparison. Agree that the 300 +tc is a nice compact and light combination, though pretty expensive.
Well, I would most likely be shooting at the long end, so with the 500, I'd be at 500. I think the sharpness of the 200-500 is great at the long end, wide open, so that gives me a point of reference. If the 300PF +TC does at least as well, I'll be happy, even though it's only 420mm.
That said, he did compare 500 vs 500, and the 200-500 won by a only few points, which was surprising (I thought it'd win by quite a bit when the 300 has a 1.7 TC). Some of it probably has to do with sample variation.
The tc 1.7EII has always reduced the sharpness by more than with the tc 1.4EII or III. I sold my tc 1.7EII a long time ago when I had my d4 and 500 f4.0g lens because I could tell that there was a decrease in sharpness compared to the tc 1.4EII. If the Nikon 300 with a tc 1.7EIII compares almost to the sharpness of the 200-500 naked then the 300 has to be an excellent lens. You will lose a 1/2 stop using the tc 1.7 on the 300 compared to the 200-500.
Larry
Hi Larry,
You may have been unlucky with your sample of TC1.7x. I am quite happy with mine on first the 70-200mm F4 and now the 300mm PF F4. Subjectively it is probably a bit better on the 200mm end of the 70-200 than on the 300mm PF.
I am done reflecting on whether the 200-500 would be more or less sharp. Fact is there would be no picture at all with the 200-500 because I would not be carrying around all the time like I do with the 300 plus TC1.7 because of the added weight. I am also very fond of the added close focus capability shown here with the 70-200mm plus TC1.7.
The 300mm PF plus 1.7TC combo is so sharp in the center that sticking it on the D7200 (24Mpix aps-c) pulls in more detail than with a similar cutout of the world with an aps-c crop of 15 Mpix on the D800. So I have a lightyweight APS-C to FF equiv. crop of 750mm F6.7. The main problem now of course is finding the d... bird flitting about on the branches LOL - my technique is lacking.
D800 and 70-200mmF4 plus TC1.7x is 340mm
The real winner I think is the 300mm PF F4 and the D7200 or another APS-C and there is quite a pick now with all excellent sensors at any price point.

D7200 plus 300mm PF F4 is 450mm F4 FF equiv
Of course you can expect worse sharpness going from TC1.4 and up to 1.7 or even 2. That is a compromise like any other compromise we have to make and you are the only one to decide which solution is acceptable to you.
The rock was shot across a lake from the identical vantage point.

D7200 plus 300mm PF F4 plus TC 1.7x is 750mm FF equiv
This humming bird landed on a thistle quite close to me and (damn Nikon) every time I clanked my big mirror it flew away 2 metres and then came back 4 times and then its patience with Nikonøs delay in launching a silent! mirrorless FF ran out and it flew away.
Because the 300mm PF is light enough for me to carry with the strap wrapped around my neck and the camera lying on top of the backpack I was ready to shoot this short-lived opportunity. Focus is more on the thistle than on the stupid bird. I like thistles

D800 plus 300mmPF F4 plus TC1.7x
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Smile and the world smiles back!