The 100YSS mission currently includes a discussion about Alpha Centauri (our closest star) as a potential target destination, but is it really the best candidate for the 100YSS?
To narrow the question's scope, I'll add that my own criteria in asking the question make the discovery of extraterrestrial life the highest priority, so I would add:
- stars with larger numbers of Earth-like planets are better than stars with fewer (in hopes of maximizing the probability of finding life)
- closer stars are better than farther stars (to minimize travel time)
- stars with more stable surroundings (like our star) are better than stars with less stable surroundings (like stars in a binary system such as HDE 226868/Cygnus X-1)