Hello there,
I had worked in engineering for a number of years and I think I can add a little to this thread which I found by accident and find it very interesting. Although I have played guitar for many years this is the first site I ever joined where the focus was on guitars. That's cool in itself.
I got my first PRS guitar a few months back. I did not pick it randomly either, I tested several other guitars at the guitar center near me which includes Les Pauls and other makes. It had good action and nice tone, and the intonation was perfect as measured at the time. It was the only guitar that had good intonation that I tried at that time, the rest needed work. The tone reminded me of an older 1959 Les Paul which I had the pleasure of playing many years ago.
Anyway, what I really wanted to point out is that in the scientific world it is never about opinion really, public opinion or other, although I also realize that in some areas opinion is all we have. In this area and the issue being discussed here though, that is not the case. We can have scientific data, and since we CAN have that, we SHOULD have that. This is the one and only way to be sure, as long as we exclude personal preference, and doing that is the only scientific, objective way.
With that in mind, the video on the PRS tuning knobs is interesting, but there's no scientific data presented. I can not think of any real scientist that would present an idea that is going to improve something without any data to back it up. The proof is in the numbers. If one-tenth of one gram difference in the weight of the tuning head or anywhere else for that matter is going to make a difference in the tone, then the data from actual real-life measurements would show that without any question. You can't argue with data as long as it is not faked, and faked data can be disproved so it's not a good idea to publish fake data.
What surprises me is I have watched this video and other videos is I never saw any scientific data. That surprises me because that kind of data proves the concept, not, "I like it this way better". There could be some data on the web though that I just have not seen yet, that's always a possibility. But anyone who claims that something is scientifically better should have data to back that up, and a lot of data, and the exact setup and measurement tools used all carefully logged and enumerated. Working with Israeli Aircraft a number of years back, the inspectors would want this kind of information on products they were purchasing, including meter makes and model numbers and other information.
Now with all that said too, I have to say that of all the guitars I had played over the years this PRS guitar I have now is one of the best. I guess that means some of those claims have to be true. I was first impressed with the bridge which I don't think you find on a Les Paul. It's obviously an advanced design and very effective. The weight of the guitar is nice too because my older Les Paul imitation weighs a ton with that thick heavy wood. I like the lighter weight better.
My PRS has metal tuning knobs. I think all my guitars have that. I am not sure if I am against plastic though as long as it is durable. I had an 1950's acoustic Gibson that had plastic knobs and pegs and that was a great sounding guitar and I had no problem keeping it in tune or tuning it.
So after all is said and done, I like the PRS guitar I have, but I do not know if the more modern ones are any different offhand. The best thing the PRS guitar company can do is publish some good data on any claims it makes. That can be irrefutable evidence unless someone can repeat the measurements and prove they are inaccurate.