For me this is a matter of personal preference. I tend to enjoy the smoothness that Bourbon brings to a cocktail. Others enjoy the spicy flavor that a rye adds. My go-to guide for drink mixing is Jacques Straub's u003cemu003eDrinksu003c/emu003e book from 1914. He simply states 'Whiskey' as the third ingredient. So it's up to you to decide which you prefer.