There is no "best" year.
The 87's are prone to CDI failure and for that reason ONLY they could be said to be the "worst" year. Other than the electrical system they're mechanically identical to an '88-'00 TW.
In '01 they got a disc front end, higher stator output and a CV carb. Quality went to heck (from an already low standard), and they lost their kickstarter. Other than that they're also essentially mechanically identical to an '87.
If you're mechanically inclined and do your own work, go old.
Not so mechanical or just in love with that "new bike smell" go new, and maintain it meticulously.
No clear winner among them.