We are all different and we all have different a different taste and achieve different results with our shootings. If I have a camera that shoots primarily color and in my humble opinion I think I have the best of both worlds, I can shoot color and I can shoot b&w.
My monochrome images are edited with Topaz B&W Effects 2, some of them with Affinity Photo. Contrary to the gentleman that stated that he has never seen a good b&w image from desaturated colors I do have seen many beautiful images treated that way and some of them were shot emulating Ansel Adams in Yosemite. I was cruising once aboard a known cruise line and I was admiring the excellent quality of portraits in b&w shot by the photographer working for that ship. The images were of excellent quality. I asked the photographer what camera she was using and she told me a Nikon set to shoot monochrome. The difference she said was that the lab working for her knew that and proceeded accordingly to print the monochrome images. We did not discuss how the lab was doing it.

My limited experience with digital monochrome images has not been bad. I have used the color image with the Topaz software and I have taken the image to a professional lab that works with monochrome images. The results have been spectacular to me. For several years I worked in a darkroom processing and printing monochrome images shot with film. Before the introduction of B&W Effects by Topaz I was very frustrated trying to make good monochrome images from digital. It took me sometime in spite of the excellent software by Topaz to find the tonalities I was used to in a good print but eventually I found what I had to do to get them and ever since I have been fine with my monochrome images. I know someone else will have a different experience to mine.

I do not use monochrome images like I did in the past and you will seldom see me shooting to convert to monochrome. If I do I know what to do to get images to my satisfaction.

I had the Bayer array removed from my A7 II (24MP) and can confirm both of these differences.

If you remove the color filter array (CFA, commonly Bayer) from a color sensor, more light reaches the sensor. A camera set to ISO 100 behaves as though it is recording at about ISO 200. But the meter in the camera reacts to that and reduces the exposure accordingly. The ISO settings in a camera that never had a color array would actually display the correct ISO.

On removing the CFA, the camera's JPEG will display a magenta image unless you also set it to display as B&W. But the camera will have used demosaicing to create the JPEG so you don't want to use it. Instead, shoot raw and use Monochrome2DNG to convert the raw file to a DNG which sets a flag to tell most raw conversion programs to skip the demosaicing process. This step is critical to obtain the primary benefit, an increase in sharpness. A camera designed to capture only B&W in the first place will already have this flag set.

When I compare the results for the converted A7 II to the Z7 (45.7MP) using the same lens, the sharpness is too close to tell them apart showing that there is an increase of about 100% in area resolution, about a 40% increase in linear sharpness.

But there is a lot more to it than just these mechanical differences.

A scene with good apparent color contrast might not actually have enough tonal contrast since two adjacent colors might have similar luminance. Although you can separate the colors during the raw conversion the side effects may not be optimal. Since this adjustment is often done to darken a blue sky, traditional color filters can help if you are using a monochrome camera but they are unnecessary if the CFA is present.

By viewing the image on the camera's LCD as a B&W image you can judge the amount of tonal contrast that will come through when the color contrast is no longer involved. This can be useful even if you don't remove the CFA and just convert the color image to B&W on your computer.

I also have the Sony a7ii converted to B&W. I agree with everything he noted. I was initially impressed with the increase resolution. There is a subtle difference between a converted Color to B&W and the a7ii conversion. I find the images from my B&W a7ii to feel and look closer shooting in film. Being a long time B&W photographer I prefer the image from my converted a7ii. I use color filters in the same way as did with film.

My used a7ii convert was about $1500. I would like to see images from the Pentax. I have seen the Leica images , As with all Leica images they are First Class, But way out of my price range. It's just a matter of taste and "do I like it"