Yes it is what is best in India's interest that matter. Ideal thing is to go in for thorium reactors which are developed indigeniously even if we have to wait for 10 years, and forget nuclear power for now.
Regarding USA or Iran, go where the commercial interests lie while not alienating either.
Gas from Iran but pipeline NOT through Pakistan. It be a long term headache for India.
An lesser known fact is that it was India that asked for the nuclear deal and not USA. http://www.rediff.com/news/2006/feb/18nspec.htm
May be a rethink over the whole issue is required.