First off, you have to define what you mean by comparing Vogtlander to Leica. Do you means lenses, or just camera bodies?
Camera bodies:
The Leica is a precision bench fitted hand assembled camera body made in Germany on a low volume basis and is very well built. It retains its value very well, and if you keep it long enough will be worth more than what you paid for it, if historical precedent is considered. A Leica can be considered an investment as well as a photographic tool. It has a much better rangefinder (longer base) than the Voigtlander, and thus can more accurately focus longer focal length lenses.
The various Voigtlander rangefinder cameras are well built semi-mass produced cameras using some "off the shelf components" such as their Copal shutters, and have good performance, and great value for the money.
Leica lenses are just about the most expensive lenses one can buy for use with 35mm film. Are they the best? Maybe, but the new Zeiss Ikon, and Voigtlander lenses are not far behind, if not equal, and are much cheaper.