Quite a few differences, most of which were aimed at making the exige good on the track..
both the clams are different (the front clam is a lot wider: it has ducting behind the wheelarch for brake cooling, the rear clam has a roof on, as well as ducts and scoops for various reasons)
the engines on offer were different (more power/less reliability);
there's currently no S2 exige (though one is rumoured),
the exige has a big rear wing,
different brakes
bigger wheels (only black alloys)
wider tyres
Aero package
built-in race-style harnesses and harnessbar
built-on fire extinguisher
As far as I know you can't get exiges any more. There *might* be an S2 or S3 exige but that's just speculation.
Craigy