I've owned a '15 Focus ST, a '17 Focus RS, and a '14 Fiesta ST, in that order. I still have the RS and Fiesta ST and right now wouldn't trade them for anything. They offer almost completely different driving experiences. As others have said, the RS feels relatively wide and heavy but is fully planted on the ground while the Fiesta is the opposite of that. The question I usually ask myself before picking one to drive is do I feel like going very fast safely or less fast with more butt-puckering moments? One would be hard pressed to find something cheaper that is more fun than a used Fiesta ST...but it is a different kind of fun than the RS for (in my case) 1/6 the cost. At that price point throwing more money at a tune and bolt-ons is also easier to justify as well, which just makes the ride even more of a blast.