I think you should take a look at the Cameraquest page here
where all kinds of finders are discussed. Although Gandy is a Voigtlander dealer, he is very knowledgeable and his site is a treasure trove for RF lusers.
The Leitz finder referred to above is the older metal version, not the current brightline version.
"Generically there are two types of Single Focal Length finders: BRIGHTLINE finders and NON-BRIGHTLINE finders. BRIGHTLINE finders have projected framelines -- the earlier finders have none. Brightlines are a later development and work better, but are more expensive (what a surprise!).
With a few exceptions, the Leitz brightlines are generally the best single focal length finders. The earlier metal Leica brightline finders usually cost at least 50% more than the later, more cheaply made, but better optical image Leica plastic brightlines. Note that only the outer body casting is metal or plastic, NOT the optics."
On 28 mm finders, Gandy says:
"For years the Leica 28 brightline was the best, but even it was bettered by the metal Voigtlander brightline introduced in 2003. It is the best 28 finder I have ever seen. I have not tried the Contax 28 finder for the new Contax G1/G2, but it is probably comparable with the Leica brightline. The best $ to performance is the Avenon/Kobalux 28 finder -- but not a brightline. The Canon is excellent, but not a brightline. The Nikon 28 finder is not that good, and neither is the Zeiss for the old Contax rangefinder. I also have a superb black 28 Komura finder (non brightline). It's optical qualities are comparable to the Leitz, but not its finish, and costs much less."
Originally Posted by andrewch
Thanks x_ray and peter for your advice. I have only used the Voigtlander 15mm and 15D finders which have a lot of distortion, and I thought Leica finders would be better. Now your advices gives me second thought. Are there any differences in terms of quality between the Voigtlander 28mm and 28mm/35mm finders ?