Fairfield Inns have a high degree of consistency. They are almost all recently built properties with the same quality of furniture and style of decor. They offer free continental breakfast.
Courtyards are less consistent. A few of them are in older buildings badly in need of renovation and are, on the whole, less nice than FIs. But most CYs have nicer rooms, furniture, and decor than FIs. Many offer a limited service restaurant or full service restaurant, though without the free continental breakfast available at FI.
I prefer CY over FI in most cases. I dislike FI's foam mattresses and cheap-looking fluorescent lights. I dislike the free, crummy breakfast, too. I'll buy my own down the street for $5.