Recently been using an MP with a .58 finder. I also have the .72 and .91 in other cameras.
The .58 is the only one that you can easily see the 28mm frame lines without contorting your eye. It of course, has an excellent view of the 35mm frame lines, and if you are wearing glasses, even better as you can still see it clearly.
But what about 50mm or longer? Well... first thing to understand is that the only difference is magnification of the VF. There is no physical difference in the actual rangefinder base length on an MP or M7 etc between the .58, .72 or .85.
So if you add a magnifier to the .58 - I'm using the Leica 1.4 - your magnification becomes .81 - and focusing longer lenses is super easy.
The .58's exposure readout does not interfere with the 50mm frame lines, so with the 1.4 magnifier you get to see the 50mm frame lines at .81 magnification with no interference!
It makes the MP's vf as pleasant to use as that on the MA. And now you know.