I know that Probox is much cheaper in built quality than fielder and there is issue with its rear seat. It is not comfortable as it is more of a loader van than a hatch back.
One other hand i owned a fielder and it is way too much better car than many of its counterparts. Consumption, pickup is mind blowing. It is 5 speed auto, good seat fabric, and lots of lots of space and little gadgets. It comes with all four auto power windows, even Altis and civic do not offer that, only driver side windows is auto.
as family hatchback Fielder is a keeper and not so in favor of Probox.