There are lots of threads on this issue if you search. Years do not matter so much with a NSX. 91-96 5-speeds use the 3.0 liter engine and smaller brakes. 97-05 6-speeds use the 3.2 liter engine and bigger brakes. 2001+ cars have the upgraded ABS system, which is nice. My ideal NSX would be a 2001 hard-top (or "Coupe"). 2002+ cars have the fixed "bug eyes" headlights.
Instead of model year, you need to think about what type of NSX you want instead. Are you a track nut who does a lot of HPDE driving on road courses? If so, the 91-94 coupes are probably your best bet unless you can find the 3.2 liter coupe unicorns out there. Light, rigid, fast and raw. Are you a boulevard cruiser who only drives the car on weekends when the skies are clear? A late model T-top may be your best option. Softer suspension, and open top make for a fun cruising on a warm night.
Also, this thread should be moved to the new/prospective owner forum.