While choosing dual sim mobiles go for Branded mobiles like Samsung/Videocon/Onida. Out of the above 3 brands only the Samsung one has simultaneous active standby for both SIMs, but Samsung ones are expensive.
Also look for the battery capacity. Anything above 1200 mah should give you a more than 4 days on heavy usage.
I am not sure, but i heard that Videocon mobiles can be officially serviced at authorized sony ericsson service centers