I would say they are very comparable. Passo's dashboard is a lot better than March and Passo has a higher roof + little more space in the boot. Options also I have seen more for Passo + passo servicing is relatively easier now since lots of em around. March on the other hand may give you better mileage since little bit smaller frame for 1000 cc, little lower on cost also, plus interior space is very comparable to Passo, however Passo is somewhat bigger. Servicing-wise, maybe Toyota 3S may do it for you or maybe not... might need to check.
It would be a good idea for you to look at the two cars side by side and make your choice based on what you like best. I don't think that March is a bad car, however its ride feel is different from Passo, and more of a classy conventional compact car. Passo is more like a compact family car in its bigger configuration + bigger cost. If you want a small car, then March is perfect. If you want more space then go for Passo for the additional money.
March / Micra Interior for you: