Thank you very much for all your contributions.
It's true, I wasn't asking a question; it was just a reflection on which I hoped to hear your opinions.
I share the opinions most of you have expressed, especially regarding having multiple simulators. I said it at the beginning: MSFS for low-altitude flights to enjoy the graphics, to be able to see the world as realistically as possible. But to simulate a B737 IFR flight, as close as possible to what a real pilot would do, I use P3D v5.4. I don't have the knowledge to judge categorically, but I perceive MSFS as an arcade game, a very good game nonetheless.
I use PMDG B737 in both simulators (for example), and my experience is that I vastly prefer it to P3D; everything from the way you press the levers, buttons, etc., the simulation seems more realistic to me.
Of course, I have P3D with a multitude of improvements: Active Sky, Asca, Toga, FS Global, ORBX Global and OpenLC, Mega Scenery, many airports, REX, PMDG, FSlabs, etc., etc., etc. For this reason, I don't miss what MSFS represents in terms of graphics, which are obviously much better than P3D.
Thanks again for listening to me and for your opinions, from which I learn.