The best year is very subjective, but if it comes down to a resale issue, the best years, long term ,may be 96 and 97 with the blue/white color scheme. Obviously this was the only choice in 96, but in 97 red was offered and it will bring quite a bit less coin than the traditional GTS Blue with white stripes.
Other years have their advantages too, with 2001 and 2002 being the only years with ABS, and getting caught in the somewhat hilarious debate over hypereutetic pistons can drag you down the garden path. The fastest Gen II dragstrip time , ever recorded , was with a 2000 RT-10 at Englishtown, with those cream puff pistons. The funny thing is folks later kept touting forged pistons as the way to go, just in case you may want to supercharge the car, and over the years the 99 became a more desirable year than when produced . Folks forgot all the rumors of a PCM change, more weight and other issues concerning the 99 , which supposedly made it the slowest of the Vipers so far. In 2000 the folks entering CAAP for tours were told of the new motor, the increase in horsepower ( not shown on paper of course ) , and Viper Days even added points to the Matrix as they felt the 2000 would have an unfair advantage over previous year models. After getting wind of this , Chrysler slam dunked Viper Days on getting funds unless they got rid of the point on the classification matrix, and workers at CAAP were instructed to no longer discuss hp gains.
Within a year or more many kept touting forged pistons as the way to go to Supercharge, even though very few were doing it, and with other supposed claims perception became reality and the 99 became a darling instead of living under the cloud it was born under. The cast pistons became cream puffs, and no one seemed to remember that the cars were quick, or that Porsche and Corvette used the same methodology on their cars.
Kinda of fun to live during periods when automotive lore and legend was being made, and when all the cards are on the table , it is pretty humorous how things became real in the end.
Other cars to contemplate would be rare colors or low production colors, and the GTS will command more money than the RT-10s. Not trying to play favorites, just listing reality. A 98 GTSR will bring crazy money, but one should likely look towards the more reasonable models , and the best advice is to get one that has had great care, preferably low miles, and depending on the year , may still be available through a Dealer for a service contract.
Best of Luck,
Bill Pemberton
Woodhouse