How Different Is the IIIa VF/RF from IIIb & Later?

[JNewell]

I always thought the change from the IIIa viewfinder/rangefinder arrangement, where the rangefinder is relatively far away from the viewfinder, to the IIIb and later where they are immediately adjacent to each other, was a plus. However, I read a criticism of the optics of the IIIb/later rangefinder that explained that the longer prism needed diminished brightness...or something like that.

Does anyone have experience with IIIa and IIIb/later cameras that have been properly cleaned and could offer their thoughts on which they prefer?

 

[xayraa33]

I have the Leica III and the IIIc, and find not a great big difference in the finders.
on both these models I use a SBOOI 50mm finder with the standard lens so the squinty viewfinder position is really a moot point.

a clean vf prizm on the IIIb and later models makes the finder just as bright as what is on the III/IIIa Leicas.