John, I'm not trying to convince you in any way...
Scores are what they are... scores. And they can be presented in different ways.
That said the 300 is behind 10% vs the 400.
The scores are actually very valuable, because they break down (exactly) where each lens is stronger (or weaker) than the other.
And actually, according to measured numbers, the 400mm is only
3.7% superior to the 300mm overall.
In actual, measured numbers, the resolution is nearly 11% better, which I agree is significant, while the bokeh and LaCA the disparity are only
2% and
1.6% better, respectively.
That is the value that measurements and tests give to the viewer, a more reasoned conclusion than a subjective exclamation like, "it's way better" ...
The measured facts verify that the 400 f/2.8 FL
is better, but the actual, measured overall superiority is quite negligible.
Even in the resolution, I am not concerned, because the 300mm is
still sharper than a Zeiss 100 Makro and Milvus. That is pretty darned sharp.
I do not choose my lenses based on scores, but rather on my experience with them under my typical expected usage for each.
I think most people, before they spend $6000 to $13,000 read the scores, and every article they can, before buying.
The scores tell you in what areas to expect performance surges/deficits.
I do have both lenses, the 300 VRii and the 400 FL. And I can tell you that they are different, being the 400FL better, should I say much better? Maybe not, but better for sure, and visible in certain conditions.
That the 400mm FL is "better" was never in dispute. You said, "way better," and that is not accurate by actual measurements.
It is between -1% to 11% better, depending on the category. (The 300mm actually has less distortion.)
I personally didn't feel that an overall 3.7% superior design warranted more than double the pricetag.
I thought (and still think), mathematically, the 300mm is the better value.
The other important impact is that mighty 100mm of more reach is essential for birds (better yet having the 800FL - on wish list), and allows the 400 to be shooted naked in the majority of the situations, not with the 300. Normally I shoot this one with the TC14III. And then it comes another piece of glass in the equation, hurting badly the 300.
I do agree with you that the extra 100mm is important. I am not sure how this "hurts the 300mm badly," but I do see the benefit of extra reach.
This is why I use the 2x TCIII.
Your 400mm x 1.4 = 560.
My 300mm x 2x = 600.
I have posted the images I have been able to achieve with this combo, and I am confident they're fine images. Are they the max possible? No. Without the TC would be an improvement, but not that much.
Nothing comes free, and the 300 is VERY "handable", not the 400. Yes you can, but for short periods.
So practical wise the 300 wins, IQ the 400 hands down.
I would say, based on pure mathematics and measured numbers, at $5400 the 300mm wins "hands down" over the $12,000 400mm practically-speaking.
Whereas, optically speaking, with only a 3.7% overall measured superiority to the 300mm, the 400mm FL wins ... "barely."
I think the 400mm isn't a practical purchase compared to the 300 VR II.
For me, mathematically(practically)-speaking, I am saving up for the 600mm FL.
It is virtually-identical, optically, to the 400mm FL ... and while it, too, is also more than twice the price of the 300mm ... the justification is the 600mm gives me
twice the reach to validate the doubling of the price
Jack