S2,3,4 are all the same in terms of cabin room - only the S1 has the small cabin.
S2/3 are very similar in that they share engine . drivetrain but the S3 has the revised lights and some other tweaks.
S4 has 4.8 engine - but interior exterior dimensions are the same as the S2/3, though there is a significant cockpit redesign with a more traditional handbrake arrangement and different vent placements.
