The best difference I can show you would be between a 50mm Leitz Elmar and Summicron (version 2) at about f/4. The Elmar gives a creamy blur but the Summicron is a bit double-imagey.
The modern aspherical lenses are generally poor for smooth bokeh. My 35mm Summarit has no aspherics and is said to be as good as the old "bokeh king" pre-aspherical Summicron - it is pretty inoffensive, anyway. However, you never get much blur with a 35mm lens unless it is an f/1.4.