I suggest used. It's hard for a lens to take so much damage that it cant warrant the better price(s)! Some people require a warranty though. To each his own I guess.
The new lenses are getting more advanced with VR, AF-S and so on,to me it depends on the lens and the price
a simple AFD design or prime is alot less of a gamble than a lens with AFS, VR etc...IMO