My usage is about 90 - 10 in favor of MSFS over P3D. In general, I believe it depends on what drives your interest in flying a sim. Kaha stated, "Aeroplane simulation to me is more important than scenery." For me, it is the opposite. I have only regularly used a handful of aircraft in the last 25 years. My main interest is scenery (as realistic as possible), flight planning including learning about the areas I fly over and using the avionics etc. to navigate while flying specific flight plans using Air Traffic Control AI.
When I tried out MSFS, it was so unfinished in many areas, that I was an instant doubter. However, once I got into the air and experienced some of the scenery around the world, I was hooked. There were so many visual improvements to the scenery that I knew right away that P3D would never catch up. Just the fact that grassy areas have 3D grass everywhere should you land on remote grass strip or in some field is amazing! So I began spending all my time making the experience using MSFS as comfortable for me as it was flying in P3D. That has taken a lot of effort but is now paying off.
I focused on the Cessna 172SP (I like low and slow flight using analog instruments) and began learning that aircraft. Since I have a rudimentary home cockpit, I then focused much of my time adapting controls and "home cockpit" start up procedures so that I would be as comfortable operating in MSFS as I had been operating in P3D.
Beginning with some fancy programming on my programmable yoke and throttle system, I slowly adapted most of my P3D add-on avionic components. I even acquired a significant upgrade to my old GPS style of control in P3D. Today I feel almost equally comfortable in the MSFS "cockpit" as I did in P3D. I miss the "slew" cheat a bit but I do like the drone which I can control using my programmable yoke system almost as well as using a game controller.
As far as scenery add-ons go, I only use Orbx distributed add-ons and a handful of specialized freeware add-ons (e.g. GNS530 enhancements, tree-distance-draw fix etc.). This helps ensure that I don't get caught in the glitches that can occur when adding lots of 3rd party sceneries that haven't been tested to all play nice together in MSFS.
There are many, many beautiful areas around the world in MSFS that far surpass P3D, but unfortunately, Southern Alaska isn't one of them. Maybe someday in a 2nd or 3rd World Update for US in the future, as Asobo has mentioned in some videos, Alaska will be improved. For now, I use P3D if I occasionally want to fly in Alaska.
In order to be fully caught up to my P3D "home cockpit" experience, I still want ATC voice recognition which is not provided by MSFS default. In P3D, I used VoxATC but that has not yet been updated for MSFS. So, I may have to look at using a different app like Pilot2ATC instead until VoxATC is released for MSFS (if ever). For now I use the default MSFS ATC system which still allows me to choose (not speak) my own responses and quickly enter the proper comms frequencies and transponder code as required before acknowledging ATC requests since it is done automatically when I acknowledge if I haven't entered the info first.
Now on to continue sightseeing around the world. See quick pic below of my home cockpit.
Rod