Thanks for these observations. This thread is giving me the perfect excuse to buy my first Mercer shirt.
Brooks Brothers is proud of their 'Six pleat shirring' at the cuff. They consider it a unique feature of a BB shirt.
By 'narrower' you mean placing the collar point buttons closer to the middle of the shirt? In fairly recent versions (2 years old) of same-sized OCBDs J. Press collar point buttons are 3.25 inches apart compared to 3.75 inches for a Brooks Brothers shirt. Of course this gives a significantly different look.