It depends on what you're wanting. I love my FiST and I bought it specifically for it's handling characteristics. Not because it was fast. I ride motorcycles and also have a 981 GT4. These all provide very different sensations.
Keeping the comparison to four wheels, the GT4 is absolutely a more special experience. The FiST is solid on-track. I upgraded the radiator, did Fortune Auto coilovers, R888R tires, tune, air intake, brakes, and have an LSD awaiting install. Stock turbo. On the track, power is the issue. I could upgrade the turbo and hang with others much more effectively, but that's not what I'm after.
The Fiesta is liveable, has four doors, it's small, and has plenty of storage. In my current setup, it's a great daily and I swap wheels/tires and I'm on-track. Running costs are relatively low.
That said, it's still a FWD hatch. The same thing that makes it a blast to drive also hinder it somewhat if you're focus is track specific.
The GT4 has better suspension. Considerably wider tires. More power. Better brakes. Better cooling. I can push the GT4 at 7/10s and run better laps than the Fiesta at 9/10s.
All of this said though, the Fiesta was a $20k car and the GT4 is a $107k car. The Fiesta is less a sense of occasion, but more fun to rip around the streets and mountains. It's about momentum, carrying your speed, and having a great time doing it. While not worrying you're going to get into massive trouble having that fun.
I ride a BMW S1000RR on-track. It's an incredible bike. My little Honda Grom for $3k is more fun tooling around.
It really comes down to your use, the roads you plan to drive, and your expectations.