I look for the best knots (tools) around for any application and use.
I think that your approach would be reasonable, in the great scheme of things, if, and only if...
...If there were a "champion", a best knot, a passe-partoot key to every knot problem.
But I have news for you : There is not ! 
Maybe I should clarify what I mean with best knot(s).
Basically I can only repeat what I said in the thread of "top ten most useful knots".
I have a small list of knots that I use for every kind of knot problem. It is like a tool box.
In this toolbox I have knots that are mostly easy to tie and remember, secure and versatile.
The list of knots I know is a lot longer and occasionally I replace or add another knot in that list.
I consider most of the knots in the list as best for their specific application.
The criteria are ease of tying, memorability, security, safety, ease of untying, versatility.
Some of those knots I think are real champions such as the zeppelin bend.
Others from the list might have a rival that is perhaps slightly more secure, but alas, more difficult to tie or untie
or
there might be a different knot that is easier to tie and remember, but alas, not secure enough.
there are still many mysteries in the working of the knot structures that are not, yet, resolved
True. For me, that is secondary though. That is my whole point. It interests me but I am more interested in the practical side.
Till then, I have an easier problem for you
: Could you please tell me the champion, the one and the only, the best, of the secure bowline loops, for example ? Because I have studied and tested all the known , I have even devised 4 new of my own, but I have not yet any idea, and I am as far of deciding as I were before entering in this small problem...
This is were we differ. I don't think I have to.
If I need a loop knot, I mostly use the simple bowline as it has a nice ratio of simplicity and security. It is an appropriately secure knot for most applications and quick to tie, easy to untie. If the application is critical however, I use a different knot such as the zeppelin loop.
When it comes to secure bowlines, I'd go for the yosemite (it has a long track record). There might be other versions that are more secure (by how much though? is it worth it?) and are they easier to tie and untie?
I am content with the yosemite but if in doubt (life at stake) I might go for the figure 8, which is still the standard knot in mountain climbing, though some sources recommend the yosemite instead as being both more secure and easier to untie. If they trust it with their lifes, it is good enough for me.