3 piece Cocktail Shaker Question
This is just my experience, but sometimes you can't get a decent pour through the built-in strainer in the top of a Cobbler Shaker, so taking off the top two parts (the little lid and the piece that has the strainer) and using the Hawthorne strainer is just easier. This is especially the case when you have things inside along with your ice and booze like muddled mint leaves, etc.