Vitz and Swift both are good cars. With jdms there’s an additional issue of low ground clearance and problem of finding parts if anything goes wrong.
Try to find a good Corolla Altis 1.6 in 4 million, not sure if it will be possible but check the rates. But your requirement is of a small car so Corolla is ruled out. However super reliable.
Passo is a worse car than Vitz, so don’t go for it.
Pkdm swift overall will be a great option if going for new GLX CVT. Good parts and maintenance support, modern with all the good safety features, great fuel economy.
If not going for Swift then second choice should be post 2016 Vitz.
Do not ever go for 2nd tier JDM cars like Mira etc, will cause huge maintenance/parts and resale issues.