I've been shooting with Nikon equipment for many years and, recently, been also using Leica body and lenses. Using Leica is simply due to getting into street photography but is also to related to using lighter equipment.
That is not to say that I'm displeased with my Nikon gear; quite the opposite. I've found it to be of an excellent quality, especially for bird photography. It's also a real pleasure to deal with Grays of Westminster, whose staff are exceedingly knowledgeable and who offer a fantastic service .... but, do I want to carry with me several kilos of equipment when it might not be necessary? Time will tell. In the meantime, I'll let you judge whether the images have been shot on a Nikon or Leica sensor.