This is an uncommon matchup i would not have expected to make sense, but in reality these cars perform similarly with some distinct differences. In terms of acceleration on paper the s2000 destroys the Fiesta ST by roughly a second and a half. In reality when starting from a roll the cars perform evenly. The turbo in the fiesta gives the car an equivalent amount of torque as an s2000. Even though the s2000 is a 2 seater it still weighs slightly more than the Fiesta ST due to its 2.4 liter engine.
The main difference between the two cars changes the entire way the car is driven when it comes to track or autocross. The s2000 has a significantly lower center of gravity and rear wheel drive. This makes the s2000 able to withstand larger forces on a skidpad and therefore take corners quicker. At the end of the day the two cars perform rather similarly unless the driver intends on drifting or perhaps making a trip to the grocery store.