@Kprasanna85 Namaste ji.
Generally , and as @Anonymous_ pointed out, it is more tax beneficial to file as Married Filing Joint ( MFJ). However, there are situations where it is tax advantageous to file as Married Filing Separate. You need to tell us more about your actual situation -- 1. are you both from the same country ( which ? ); 2. Is one of you have substantial foreign income that you want to keep away from US taxes; 3. one of you have past child support/ state-fed tax debts, judgments etc. etc. etc etc ?
As @Anonymous_ said ,for most people, even if you are NRA, MFJ is usually the preferred filing status.
Please provide more details of your particular situation --yes?
pk
