My opinion :
-- Vitz has more stability and gives driving confidence swift lacks this aspect poorly
-- Swift suspension is most comfortable i've experienced in small cars and i really love it (i own a japanese swift so can't say if pakistani version is different)
-- I'll vote for interior of swift as vitz panels and dash is totally scratch prone and a few other aspects
-- Both will compete neck to neck when it comes to fuel average and acceleration, but i think vitz will lead here by a little margin
had it not been for the poor stability my vote would've been for swift but jumping jack attitude after crossing 100kmph makes swift dangerous ... buy vitz