*my reply is based on NOT seeing the actual car and NOT knowing/meeting the owners*

Magkaibang tao may ari ng 1.3 and 1.5 - obviously mas mahal yung 1.5

Pro 1.5
mas malaki yung chance na nasunod yung PMS nya
bigger engine means even if the loss of power due to normal wear and tear, baka same power lang sya ngayon when the 1.3 was new
better features/better interior materials than the 1.3

Pro 1.3
malaki yung chance na first time car owner, so iningatan ng husto yung car/malaki din yung chance na ginamit as PUV
smaller engine, if naka-idle both cars in traffic for an extended time, I'm sure mas matipid sya sa gas.
BUT (based on experience) if stop and go traffic, depende sa driver, minsan mas matipid yung 1.5
Ang daming gumamit ng 1.3 version ng Vios... so engine parts are easily available