Originally Posted by retiredmd

Permit me to answer your query. Understand that I held NHRA (National Competition/Super Street) and SCCA (National Competition) licenses before most on the Board were born. In years past, I attended nine Racing/Driving schools, joined several Racing Clubs, was fortunate to drive on tracks from Long Beach to "The Ring", organized formal driving tours throughout Germany and Switzerland and served as Instructor during a number of driving events sponsored by PCA and BMWCCA. And, oh yes, I was a maniac before retirement, owning six 911 Turbos, three 911s, three NSXs, a ZR-1 Vette, Viper RT/10, Lotus Espirit S4S and a Callaway TT Vette. And those were just my sports cars. My "family cars" included two M5s, two E-55 AMGs, a C-63 AMG, a C-32 AMG, an M6, a MB 2.3-16 Cosworth, etc.
The point of all this is that I have some experience to intelligently discuss the matter.
Now, from a general performance and handling standpoint, a new Nismo's additional cost above a base/sport model is NOT justified. For one thing, when stock, the Nismo is fractionally slower in acceleration runs because the stiff rear suspension will not permit the car to squat and hook-up off the line. Hence, the addition of after-market goodies to a base model will produce a noticeably faster car than a stock Nismo and still cost less.
As to handling, there ARE differences between a Nismo and base/sport models-some good, others not. The Nismo demonstrates slightly better on-center steering feel, feedback and response (wheel/tire package the likely reason), better turn-in and far better rotation and superior in inducing very easily controlled drifts. I found the base/sport model superior in the ability to steer with the throttle, take a line without having to correct, tolerance of trail-braking and decreasing-radius turns. All-in-all, a novice would find a base/sport model more forgiving and faster around most race and road courses.