ST-2 has:
Recaro heated sports front seats with partial leather trim
Halogen projector style headlights with LED day running lights
Sony DAB audio with SYNC and Emergency Assistance
Ford power starter button
Privacy glass
ST-3 adds:
Sony DAB Radio/CD with Navigation System
Ford KeyFree System - Keyless entry with Ford Power Starter Button
Cruise control
Automatic headlights
Automatic wipers
Auto-dimming rear-view mirror
Electronic Automatic Temperature Control
Power-foldable door mirrors with puddle lights
I believe all of the above can be added to the ST-2 at time of the build, I've got some of them on my ST-2. So the car you're looking at might have some of these anyway.
Some of the features would be nice as standard, but not a deal breaker if you don't have them imo.
Recaro heated sports front seats with partial leather trim
Halogen projector style headlights with LED day running lights
Sony DAB audio with SYNC and Emergency Assistance
Ford power starter button
Privacy glass
ST-3 adds:
Sony DAB Radio/CD with Navigation System
Ford KeyFree System - Keyless entry with Ford Power Starter Button
Cruise control
Automatic headlights
Automatic wipers
Auto-dimming rear-view mirror
Electronic Automatic Temperature Control
Power-foldable door mirrors with puddle lights
I believe all of the above can be added to the ST-2 at time of the build, I've got some of them on my ST-2. So the car you're looking at might have some of these anyway.
Some of the features would be nice as standard, but not a deal breaker if you don't have them imo.