https://www.youtube.com/watch?v=mQKLPTur8HQ

video description

Sony seems to have quite a bit of variance in console fan noise even within the same model if we go by user experiences (or some people are radically more sensitive to it than others) - I think a single test is not enough to determine whether the model itself is more silent or not.

And atleast in the first PS3s they used a shitty thermal compound which deteriorated with heating/cooling cycles and therefore necessitated faster and faster fan speeds (= more noise). I'm not sure if they use better stuff now, but my PS4 seems to not get louder with time (it's noticeable, but not annoying imo).

After taking off the 60GB PS3 IHS and changing the thermal underneath and above, it was the quietest one i owned, never went past level 3 fan noise.

it is different hardware https://www.youtube.com/watch?v=JtWy-eAGIew#t=4m40s

This was known already...it also uses less energy. It's optimised hardware, more efficient and cheaper to produce, the way Sony always do it with their hardware.

My matte white PS4 is also much quieter than the original model with the glossy parts.

OP fix your title there is a typo. You got quite instead of "Quiet"

Doesn't mean much. Sony use 2 different brands of fan to cool PS4 APU. One is very silent, the other very noisy. Maybe by chance the 7100 model on the video has the good brand of fan and the 7000 the bad.

This doesnt really mean much, cause fan noise varies wildly from PS4 to PS4. You could luck out or get a silent one (which happened in this case, and is very rare), or you could get an embarassingly noisy one (which is also somewhat rare).

Hard to say based on one comparison.
My friends Star Wars 1200 PS4 is pretty quiet. You can just barely hear the high pitch whine of the fan here and there. His console sits horizontal. He bought his a few weeks before I bought mine from the same store.
My Uncharted 1200 PS4 is quite a bit louder and the whine is much louder and comes and goes a lot more often. It sat horizontal as well. I've applied new MX4 paste and that helped a little. I tried the console in a vertical position and its just as loud as before, but the whine is basically gone now.
The stock paste on my 1200 PS4 was decent quality and was in good shape after a year. I also had the better quality, supposedly quieter fan brand as well, which was odd since I assumed that my buddy probably had the better fan and I had the worse one. The whine my fan made, only started after a couple months of use btw.
I even had a good look at the heatsink to see what kind of imperfections it might have and it was very flat and machined very well. I could have polished it down and allowed slightly better contact, but I don't think it would have made much difference since it was pretty smooth already.
I've heard a couple other PS4's close up, a 1000, 1100, and 1200. The 1000 was fairly quiet, the 1100 was as loud as mine, and the 1200 was jet engine and had a super loud whine. I really do wonder if it has to do with a mixture of day to day assembly, fan brand and quality, as well as varying chip quality.
My PS2 and PS3 slim were both dead silent. My PS4 never goes jet engine, but makes noticeable noise. The whine was irritating and bothered me, but now that its gone and just the natural fan noise exists, its not really a big deal.

My PS4Pro is very quiet. I never hear it making a sound when watching movie or playing games. Then again, I keep it clean and well ventilated.