There are not a lot of significant changes in the Viper since 01. Cast pistons in 00 and ABS in 01 are the major ones. Your choice should probably come down to these issues:
<UL TYPE=SQUARE>
<LI>Old vs New -- Do you want a car that you absolutely know that wasn't abused and is in perfect condition? And are you willing to pay for that? Or is the option of saving $15-20K or more over new more palatable?
<LI>Color Choice -- Since 96, there have been only 2 or 3 colors available each model year. If you want a Blue & White, it's 96 or 97. Period. End of story. Same for 98-99 if you want silver or 99-00 if you want black. (Of course, you can get Red any year.)
<LI>RT/10 vs GTS -- This is a religious choice. There are lots of fervent opinions for each.
[/list]
The Viper's not like, say, a Z06 Corvette, where, if you rushed out and bought that 2001 Z06, you're now wanting to unload it and get a 2002 because there will be an additional 20 HP. There are some differences between a 1996 and a 2001, but not enough to really dictate a choice. (OK, maybe ABS, if you can't bear the thought of driving without it.) So if color choice is very important, you can let that dictate the year and not worry about if the new ones are better.