We have only W2 incomes, use standard deduction, with no dependents.
My husband works in NJ making 11k, I work in NY making 6k.
I am not sure to file married jointly or married separately for NJ and NY state tax. Which will have the highest tax refund? Can anyone give a rule of thumb?

If you and your spouse each have income, you may want to figure your tax both on a joint return and on separate returns (using the filing status of married filing separately). Choose the method that gives the two of you the lower combined tax.

Normally, states require that you file in the same way you filed your federal tax return. For the state you are resident, you will report your income. In the state you are nonreisdent, you do not report any income. Your U.S. Tax Return: Working or Living in Two or More states

I have a similar situation to yours. I filed Married-Jointly for Federal, and separate for State. Turbo Tax showed me both figures and which one brought home better results.

Your situation may be different.