Which country is better to import from, India or China? Any negative/positive feedback for both?
Each have their pros and con's , just do your research, and find the right seller.
What is the import duty on importing in US? Can this be avoided for smaller quantity?
Its all based on the value of the items your importing. To get exact rates, call up to the shipping company your going to be using and they will give you their %'s of their rates for brokerage, duty,s Taxes. As for avoiding the duties, that's illegal technically. Now, when purchasing most companies that have licensed brokers will or can offer you FOB CNF prices.
What is the most efficient mode of shipment while importing from these countries?
None really efficient, now china uses EMS, their local postal service. Most European companies stay away from the big box stores like UPS and Fedex cause fees are restarted sometimes for their customers and it kills deals.