Lisitsa, if I understand the question right, then an un-used bike implies new components and everything else, whereas a used bike is a second-hand 'used up' machine. Rust is the only enemy of an un-used bike, other than that, it should be the number one choice . . . But heck this sounds like an addiction to me :-)
By the way, do the bikes fit you 100% OK? Cheers.