When you see product comparisons you know that one is better than other and is more obvious when there is a huge price difference in between. But you always want to know what you are missing from the better one and make a choice if one is a better investment over the other based on your personal needs and preferences.
So, I started shooting with the Voigtlander Nokton 50mm Aspherical Silver and this is one image from it:
But at some point in time I was shooting with a Summicron-M 50mm and was surprised of its image quality so I had to do something about it. That is when I invested in the Summilux-M 50mm Aspherical, the following image is from the latter lens:
Is when I decided to make side by side comparisons and this is what I found:
I see better definition and better color. Now, is up to you if you decide that one lens is worth its premium. Remember that even a cheap $100 50mm Nikon AF-D can make great images. Access, composition and the action are what make an image for me. Gear becomes secondary.