Street Photography: Olympus 17mm F1.8 or Panasonic 25mm F1.4 ?

I am not sure I follow you

I'd rather go with the classics, and don't ask permission, ever. Focal and FOV are therefore completely dependent on how good you are at approaching a fleeting subject.

HCB's Images a' la sauvette, literally means: without asking permission.

From HCB's 'The Decisive Moment' introduction:

"In 1952, Cartier-Bresson published his book Images à la sauvette, whose English edition was titled The Decisive Moment. It included a portfolio of 126 of his photos from the East and the West. The book's cover was drawn by Henri Matisse. For his 4,500-word philosophical preface, Cartier-Bresson took his keynote text from the 17th century Cardinal-de-Retz: "Il n'y a rien dans ce monde qui n'ait un moment decisif" ("There is nothing in this world that does not have a decisive moment").

Cartier-Bresson applied this to his photographic style. He said: "Photographier: c'est dans un même instant et en une fraction de seconde reconnaître un fait et l'organisation rigoureuse de formes perçues visuellement qui expriment et signifient ce fait" ("Photography is simultaneously and instantaneously the recognition of a fact and the rigorous organization of visually perceived forms that express and signify that fact").

"Photography is not like painting," Cartier-Bresson told the Washington Post in 1957. "There is a creative fraction of a second when you are taking a picture. Your eye must see a composition or an expression that life itself offers you, and you must know with intuition when to click the camera. That is the moment the photographer is creative," he said. "Oop! The Moment! Once you miss it, it is gone forever."

BTW don't put words in my mouth: I never advised to use 'long lenses', just the opposite. The more you dare the shortest you can go, a well known fact among street shooters.

Am.

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Photostream: http://www.flickr.com/photos/amalric