Fascinating blog post at lensrentals.com
Today’s word: measurebating
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Intersting… Though “this lens is working well for me” is completely qualitative and “zooms is better than prime” is quantative… I don’t think you can compare the two statements.
My lensbaby works for me completely… But the quality is terrible. 
I think the message is that haggling on zooms is pointless because there is too much variability in zoom defects. In fact you don’t know what you buy… Primes are not only somewhat better, they are also a lot more constant.
yeah, great article indeed. especially when it comes to comparing zooms of different manufacturers! 
)
If only I can distill this kind of scientific reasoning into my students. The world would be a much better place. Thanks for sharing this link!
I found this little part interesting:
“If you ask me to pick you out a really good copy from this set of lenses, I will send you any of the three diagonal from top left to lower right. (Just so we get it out of the way, if you wonder what it costs for me to test 9 lenses and pick you out the best one then you can’t afford it.)”
While it should be clear that anything manufactured is going to have variations from one instance to another, I wasn’t aware that checking individual lenses was an available service. I did a quick search of the major camera retailers in my area, and none of them appear to offer such a service.
If it would be good to make sure you are getting a decent copy of a lens for rental, it would be very good to make sure of that when buying a lens outright. Maybe the “you can’t afford it” consideration applies. 
I remember that i first time heard this word - measurebating - on ken wheeler (theoria apophasis) youtube channel. Anyway, primes (especially those with low elements count) are so better than zooms in any way regarding to image quality, and your feet are the best zoom lens! Never used a zoom for my dslr or mirorless. In fact, never got one!
I also prefer to use primes over zooms. I use primes for about 95% of my shots. But there are also situations where you can not zoom with your feet (being on a boat, standing on a cliff etc.)
I bought a Samyang 35mm last year and was disappointed with the sharpness. It went back to the UK agent/distributor for Samyang, Intro2020, and they were very happy to tune it up, and it was a lot better when it came back. They seemed a good outfit.
I use a cheap light standard kit zoom as an everyday walk-around tourist lens. When i know what I am going to shoot, I use a prime.
I also only shoot primes. I do have a weather resistant kit lens in case of terrible weather and must take photos, but I’ve barely used it. (it came with the second hand camera I bought).
Thing is for me primes are not strictly about quality. I just really prefer not being able to zoom and I very much like the small size of the primes available for my Pentax camera. The directness of shooting primes after years of zoom lenses was quite the revelation for me. The quality bump is appreciated for sure but not the main thing for me.
Unconsciously the Samyang 35 1.4 has slowly become my “always on” lens. I can’t tell why, but I like its shots always better than the one from my “supposed to be always on” Tamron 17-50 2.8. Must be the time to prepare the shot (even if it’s a kid’s portait) that exacts a proper framing as well as its nice bokeh and color rendition.
Never known how to zoom with my feet (except to reproduce a flat subject)
Never found a x->y zoom heavier than x prime + y prime, nor slower than umount x + mount y
But it is true that many zooms produce poor image quality!
I find the tests he dismisses useful and view them before i buy any lens - if I can. I also find that they do give an idea of what to expect from a particular model. How do I know - I’m a pixel peeper. I may also look for a raw file taken with one or even a full sized jpg if that isn’t available. Pixel peaking raw isn’t as attractive is it was though now. A number of camera have such high pixel densities that the lenses haven’t a cat in hells chance of resolving to that limit. That allows them to drop the anti aliasing filters from the sensors which may even produce better pictures but is also cheaper.
Personally I hardly ever shoot primes. Just macro really but that’s experimental and I have taken lots of those using a zoom and an achromatic close up lense. That’s down to using m 4/3. Their macro lenses have too short a focal length for easy use so my macro prime is for a crop camera.
When I buy zooms I do my best to go for ones that don’t exceed a focal length ratio of 3:1. Gets tougher as time goes on as the buying public want more - or the manufacturers think they do. At the rather wide angle end the ratio needs to drop to 2.
John