V-Spec differs in all models and is not just a trim issue.
R32 VSpec offered (over and above its no VSpec counterparts) 17X8 BBS style alloys, Brembo brakes front and rear, lower/stiffer suspension and vastly improved handling.
R33 VSpec included better suspension, wheels and tyres were common, and Attessa ETS PRO which offered considerably better roadholding ability.
R34 VSpec was a similar deal with the later V Spec2 having different rear brakes, alloy pedals, carbon front and more.
So to answer your question, V Spec itself is simply a higher level of specification from which better performance (usually handling) can be had.