I'm not even gonna hazard a guess. To the extent we'd ever see the difference, it would be in a really low light shot or some hyper DR shot that really challenged the limits of the sensor. For this type of shot, particularly at this sort of viewing size, there should be no visible difference. And any difference we would see wouldn't be the result of sensor size...
This is not about high is or dof control. But it has been said that the Nikon Df sensor is the best all round sensor to beat. That it shows exceptional color rendition, tonal gradation, highlight and shadow detail. And it does. It has been said that the Fuji x-trans sensor shows smearing and watercoloring effects with greens/leaves. It has been said that the Fuji X-T1 comes close to the Nikon Df and might even beat it: http://www.whatdigitalcamera.com/ro...-t1-vs-nikon-df-sensor-and-dynamic-range.html
I have a loaner X-T1 with the 35mm lens and wanted to see see how it compares with the Df with its kit 50mm under "my shooting conditions". I did about 30-40 comparison shots (all raw) yesterday and could not see any smearing issues with the Fuji files. What I saw instead, is the smaller camera holding its own against the FF Nikon. From the Nikon I prefer that it is instantly ready to shoot, the OVF, the faster and very reliable AF and its more predictable metering. Size and weight advantage speak for the Fuji and the "analog" user interface of the X-T1 coupled with lenses with aperture rings is fantastic. Both cameras are excellent and shooters cameras. Fuji has come a long way since the X-E1 which never grew on me.
both look good - there is also the D800E to consider
small v bigger
I have just added a grip to my D7100 and it feels a lot better now that it is bigger
I added a grip to my Nikon V1 and it is still too small
I don't have big hands but the controls on these smaller bodies are just too "fiddly" and small for me
I have detected the "watercolor" effect from Fuji files, but it depends on how you process them and the size you view them at. I process with Lightroom and at 100%, you can definitely see it. I've played around with Photo Ninja and it doesn't happen with that. But at the sizes I tend to view and print at, I can't see it regardless. So, to me, it's a non-issue. And you'd certainly never see it at the sizes you posted at here. I'd still say the Df sensor is better than the Fuji, particularly at high ISO and particularly if you take a bit of Fuji ISO inflation into account. But, as you say, the Fuji definitely holds it's own - I decided to go with Fuji after shooting extensively with the Df. Not because I thought it was better, but because I found it close enough to as good. And comparing Fuji's excellent primes against the smaller, slower Nikon lenses I'd have been willing to use with the Df, the Fuji more or less matched it even in low light. Different story if I'd been willing to shoot with the big fast Nikon primes, but I wasn't.
I'd agree that Fuji has come a long way since the XE1, but NOT in terms of sensor performance. In terms of AF, MF aids, operating speed, features, EVF, yeah, much much better than the XE1. But the sensor is basically identical minus a few pixels that are used for PDAF in the newer bodies and weren't in the bodies before the XE2. And they have released a few more lenses since the XE1 and the new Fuji lenses are incredible - even better than the original three, which were already pretty great. But in terms of sensor performance, they're basically the same...
There is a difference in perspective. In both cases, the first image looks deeper. That indicates a wider focal length and thus the APS images. They both looks great, but it depends on what your intent is.
I agree 100% that there is a difference - in fine detail, in tonal response and most importantly for me in size and weight. The last reason is why I sold my 5DII and lenses and am currently shooting with just an X100S and an E-PL1 with legacy glass (when I need something longer than the 35mm FOV). I intend on picking up an X-T1 at some point though.
"A difference which makes no difference is no difference."
I can see one between medium format and m4/3, but between aps-c and ff, I honestly can't.
As I have said before, a good big 'un will always beat a good little 'un, but this is akin to comparing a light, fast spotscar with a larger, heavier GT. Both are the same, 0-60, but their differences show when you live with them. I lived with a D700 for a while, and with big and heavy film SLRs before that.
Life's too short.
Go with what works for you, secure in the knowledge that in the real world you are yourself the biggest differentiator in the entire image capture process.
I'm sure everyone would agree that a full frame sensor, like any sensor, is only as good as the glass you screw on the front allows it to be
Apart from the obvious depth of field , I have found the Sigma DP Merrill's absolutely trounce the 5D mk2 in detail if nothing else. I even prefer the results from the Sigma's to the Sony RX1 I had briefly . This is all subjective I know.
Now if Sigma produced a full frame Foveon I would go there in an instant . Even sacrificing high ISO capability and speed of use.
I do agree with Duane though about full frame. As long as you can use the very best lenses you can get.
...and as long as you mount your camera on a tripod, or hand-hold at a high shutter speed having not just exerted yourself or drunk an espresso, or alcohol, or...
The point is there are many links in the optical chain, and the individual pointing the camera is, in most real-world usage, by far the weakest link in that chain.
For me it is this simple. I will carry a film Leica M all day, but not a digital. I will carry an X-T1 all day but not a DF. I am no seven-stone weakling, by the way - I am 6'3 and well-built - If a camera is too bulky or too heavy it will stay at home - that is exactly the fate that befell my D700, now long-gone.
If ultimate image quality is the goal then I would suggest that medium- or large-format is the way to go... But of course that is impractical for most day to day use...
Where does it end? With your own PERSONAL threshold, which, I would suggest, varies with time and circumstance.
In short there is no absolute, definitive right answer to all this, outside of laboratory conditions. The solution that is right for YOU is RIGHT for you.