i'm currently driving a 1 mth old Lancer Sports Manual. Dunno
how you guys managed to get FC around 15km/l. Must have some super
secret fuel saving driving method. For me, the best I've managed is
14.3, but on the average, I hit about 13.4km/l, which I'm quite
happy with. 
The following are just MY opinion:
LANCER (Pros)
1) Spacious interior
2) Good FC
LANCER (Cons)
1) Recent PR hoo-ha (i dun really care)
2) uses 4-year-old technology (GLX)
VIOS (Pros)
1) Speedy pickup/acceleration
2) New modern technology (VVTi)
3) Probably higher resale value
VIOS (Cons)
1) Cramped back space (i mean, very cramped)
Vios is good if you're driving alone, or with 1 front passenger
most of the time. Quick pick-up, sporty, lots of aftermarket stuff
etc. But if you need to ferry friends, family etc and use the back
seats very often, you'll have to seriously consider the mild
"discomfort" of the cramped rear.
Eventually, I picked the Lancer. 