The 35mm is the king of shooting in close. Of course you have a wider field of view but you also have more depth of field. When the subject is closer more depth of field is very advantageous to keep all of the subject in focus. It also covers for focusing errors that occur because if the subject is moving and if your not experienced with manual focus, it can be difficult to get an in focus image. Even a slow walker can be difficult to shoot within ten feet with a 50mm because subject movement is magnified. The 35mm is great for shooting people interacting with each other or the environment. That being said 35mm portraits are often not that flattering. Unless you are careful with what is on the edges of the frame you can end up with wide angle distortion.
The 50mm is great for detail work. I don't mean close up or macro work but the details of life. Look at the work of Leica master Henri Cartier-Bresson. He was so great at framing the action so that all unneeded elements are cropped out of the frame. If you are more of a purest and don't like cropping the image after you take it, the 50mm is for you. Because of the wider view of the 35mm it is more difficult to keep unwanted elements out of the frame. Although I prefer longer lenses for portraits, the 50mm is great for environmental portraits. Again, refer to Cartier-Bressons book of portraits. The are among the best ever taken. Mathematicaly the 50mm is the view that corresponds to the normal view of the human eye. Some like the straight forward vision this lens gives, no distortion of a wide angle and no image compression of a telephoto.
To help choose between the two lenses the best metric might be just to look at your own work. Fire up Lightroom or your program of choice and look in the info panel to see what focal length you prefer with your favorite images that you might shoot over with a Leica. The results might even surprise you. It is best to buy a lens that matches how you shoot now, not how you think you want to shoot. If you are at the point of putting thousands of dollars down on a body and lens it is best to match up with your current style so that you will grow as an artist.