You'll get later model Passos in the prices lesser then that of Vitz,
Passo was a question mark but the second gen Passo makes it be in the market for alteast next 5 years, The car shares the same engine as of Vitz (1krFE ) and now both cars have the same CVt transmission too.
Passo had better acceleration due to being non CVT and a wired accelertor in the first generation, Im not sure if the new Passo has a wireless accelerator or not, But its CVT for sure.
Passo isnt avalible in other countries a similar model is avalbile in Malaysia as MYVI but it still is a alien car in too many countries, While Vitz is avalible as Yaris in Asia and Europe aswell, Which makes scrap cars coming in much more easily and in huge numbers thats one reason why Vitzes spares are cheap and they can be brought brand new from Taiwan and China, Im not sure if thats the similar case with Passo or not.
In case of Vitz, the most major parts can be purchased over night from Dubai, Passo lacks this advantage, But yes the money saving is a big reason to go for Passo and its any day better then buying a Mira. Id say go for a decent Passo if you find one. A similar model Vitz would cost atleast 1-1.5 lacks more.