I'm a NY State resident who got married in Nevada in July of 2011. How do I figure out if it is more advantageous for my spouse and I to file married jointly or married filing separately?

You prepare returns in both ways and see which is more advantageous. There is no magic formula BUT filing separately is USUALLY more expensive.

THANKS

In most cases, it is better to file as MFJ. If you file MFS, you will not get many credits and deductions including EIC.
On the joint return the liabilities are joint. For joint return, after the due date you can not amend your return to file separate return. Your U.S. Tax Return: Filing Status for Married

Agreed; filing jointly is almost always the better option.