the optra is a korean car. but it's bigger. the vios would hold its value better if you intend to sell it after a few years. but if you intend to keep it forever, the optra is more car for the same money. reliability is more suspect though (korean vs japanese-but-made-in-thailand).

personally, i'd go for the optra. the vios is cramped and noisy on the highway. the optra is supposed to have pretty good sound insulation though not as good as the ford focus.

also check if the optra's computer has been reprogrammed. you can save quite a lot of fuel that way.