"BTW Bikerz buy S15 coz it handles better, sexy, better accelaration than GTT ( not GTR ye..) and it depreciate lesser than GTT."
are u sure? ... please do the homework before putting such statement dude!
Actually it is true except the depreciation part, its more or less the same with a GTT.
As for fuel consumption,
when my S15 was mildly modded (full turbo back exhaust, fmic, walbro fuel pump, 1bar boost),
I got 460-500kms per full tank for city driving and 600+kms (highway).
Stock for stock though, an S15 spec-R manual will win a GTT manual everytime while dragging (0-400m).
But at higher speeds, the GTT feels a little more stable than an S15 due to the extra weight.
Mod potential, both also can go fast if you have the cash. Haha.
But always remember, there's no replacement for displacement.