Looks are subjective so theres no right or wrong. Personally I
find the Vios better looking than Altis, especially its back and
the tail lights. Altis looked more matured and steady while Vios
looked younger and energetic. Altis is definitely larger than Vios
in size (24.5cm by length, 1cm by width, 4.5cm by height).
Interiorly, Altis also appeals better with its refined look and
cabin space as its targeted at the executive segment.
Speedwise, it has been claimed that Vios is still steady at speeds
up to 160km, and of course I have no doubt the Altis can do so too
by virtue of its heavier weight, even though I dont believe a
heavier body can protect passengers any better at such high a
speed. Body roll of Vios is admittedly quite bad so its not good
at turning fast corners. Id prefer to drive the Altis than Vios if
I travel often in Malaysia.
Vios can match, if not beat the Altis 1.6L in acceleration even
though its a 1.5L car due to its lighter weight. Stock Altis is
120kg heavier than the Vios, so its like carrying the weight of 2
more adults in every trip. Consequently, Altis fuel economy is
poorer than Vios as both have similar VVT-I engine
technology.
Altis price is about $8K more than Vios, with higher road tax and
insurance to pay along too. Personally I dont think its worth
paying such premium for the Altis over the Vios, but we are also
not really comparing apple with apple here. 
