I've the 4.2 GTS and to knowledge its the only one in NI. Sport mode holds revs up to 7k and shifts 33% quicker, in addition to firming up the springs. As a sports car, The GTS is superior over the Sport GT or Executive because of the lower ride, wider rear wheels, 6 pot brembos and remodeled seats. It's also a bit lighter with the a carbon dash, gearknob, door panels etc.
Above all the GTS has a meaner stance with red calipers, black window surrounds, black exhaust tips, 20" wheels, black grill and lower ride as mentioned.