That Canon or Nikon 24-70mm f/2.8 is a great lenses, covers most of the focal length you would want and need for most of your life but for me, that lens is missing one important thing for my style of photography and it is bigger aperture. Even one stop difference from f/2 to f/2.8 you are looking at ISO 3200 vs 6400 and if you really need a bit more for natural light add a two stop difference ( f/1.4 to f/2.8) and you are looking at 1600 vs 6400. Some modern cameras of 2015 can shoot above 6400 and still produce usable results but as of today I don’t shoot beyond 6400. I am also forcing myself to shoot with wider lenses and create compositions using the background in harmony with the foreground. I would like a Summilux 28mm f/1.4 but in a Summicron size and since that won’t happen I am reviewing the 28mm Voigtlander Ultron f/2. The lens isn’t very sharp at f/2 but gets sharper than the 24-70mm at f/2.8 but then it suffers from little focus shift at f/4 through f/11 so until I save for that Summicron 28 or give into the bigger Lux 28 I will shoot with this Ultron.
Below is a comparison to the sharpest lens I have access, the Lux Aspherical 50mm, it produces very organic neutral color, amazing detail and marvelous control of blurred areas while the Ultron gives you a cooler temperature rendition and less color control.