Hi everybody. After all the help and advice I received on this forum I thought only fair to give an update on my decision.
It's been a difficult decision as the choices were quite tight, and now with Apple Silicon coming it's one more factor to consider.
I decided to stick with 13" because in 80% of my average use it behaves really well fan-wise.
It only goes full hairdryer (6k rpm fan noise) in specific use cases (if I'm doing processive intensive tasks and time machine or other similar background process is running or when I have a virtual machine or if I watch a 4k video on YouTube regardless of the browser; yesterday watching the WWDC keynote meant fans at about 4k rpm: not airplane, but you could definitely hear them).
Of course such use cases are important and of course one new latest generation top of the line mach should NOT do that. But this is the world in which we are living in. If you get a 16" you will get more or less the same situation.
The 16" is maybe a little less noisy when using only the internal display, but a little (or much) more noisy if using an external display.
With this generation of apple laptops (air, mbp 13 and mbp 16) the fan noise is inescapable. It's just the way it is.
I suppose this is part of the reason why Apple is switching to Apple Silicon.
To summarize my reasoning: I preferred the 13" when I had to choose the laptop size. After it arrived, I discovered it was more noisy then predicted. I discovered that also the other alternative laptops were more or less the same. Therefore I will stick with the one I have which is bearable, even if significantly noisy under certain usage conditions which are not rare at all.