Based on technical specs, Vios has a slightly lighter chasis and its engine outputs slightly more power than the city.
Sorry just had to state that power at the engine does matter but the one that gets you going is power to the wheel. So that's the reason the City is more powerful.
Though marketing people will use the 110ps and 109ps crap. They don't show you the loss at the aircond, gearbox, the power steering.
Anyway.. these things are quite silly. Its up to the buyer. Don't know why people would shout and say VIOS boleh.. and HONDA boleh. What's the point of just shouting without facts?
You can guide the buyer but it is his choice. You don't want to screw it up for the fella. To most VIOS people the looks seems to be the most important decision so.. never judge a book by its cover :). But I have found some like my colleague who wanted to purchase a honda but because of the price bought a vios. And another because of space bought a city.
So don't confuse others. Point out your facts and let them decide. You don't want them to suffer later just because you are a die hard honda fan or toyota fan.
r'gards