Not the same car I know but the Bilstein'd 500 I've been in had a terrible ride...
You've got to take warranty and insurance into account too. The Assetto Koni kit has a two year warranty from the date of installation, if you have your top mounts fail (which lets face it, they will) then Abarth will void your warranty if you're using coilovers. Insurance is less too as it is an official optional extra rather than having a coilover kit fitted.
As for the design comment; the Assetto Koni kit is actually available for a standard APE, as well as the Supersport. They come in the APE SS kit as well. Not just relegated to 18" wheels