yara i have driven both and trust me, japanese alto is way better than the local one in every aspect, be it engine power, economy, engine response (pick you may call), comfort, sturdiness of suspension, cabin room etc. despite the fact tht its just 660 cc as against the local's 1000 c.c engine. moreover, its completely power packed with abs and airbags etc.
however, am not sure about the availibilty of engine parts. but i am pretty sure tht the maintenance parts must be common like filters, plugs etc.