Here's the front exterior of the SW model...
Here's the front exterior of the SX model...
You'll notice a different bumper, grill and headlight/foglight treatment. The SX has a deeper grill, 'larger' headlights with a different arrangement and appearance. Different bulbs are used in all cases compared to the SW. The front bumper has been redressed, losing the cat like appearance with the single 'fin' from the SW removed and three horizontal bars in place.
The exterior, for Australian models are identical.
Engine, in Australia is the same 2.5L Duratec V6 across all models and variations (includes Eibach).
Interior, SW:
Excuse the Americanism, the DVD screen etc... but the black/grey/silver scheme is standard in the SW. Grey dials, silver rings around the a/c vents, silver middle section for a/c controls. Steering wheel is sort of a rectangled centrepiece with small Cougar logo.
SW Seats.
SW Rims.
SX Interior. Notice the different steering wheel with larger Cougar logo, white dials, grey all over instead of silver touches. The speaker grilles in the front doors get a polished aluminium ring around them (no ring in the SW's).
New seats with larger bolsters.
SX Rims - Australian versions have Ford logo, not Cougar logo. 'Ribbed' appearance instead of flattened like the SW.
I think they're the main differences worth noting. Aside from body panels, and some interior changes, the cars are the same. Rear seats, boot space, rim size, ride height and comfort are unchanged.
Except with the Eibach Cougar, which sits lower, has different rims and a bodykit.
Hope this helps a bit, it was a rushed effort to put this together.
Dan