In general, filing out your filing status on Form W-4 should be the same as the filing status you use to file your personal tax return as of 12/31. If you would like to have more taxes withheld from your pay you can keep the filing status on Line 1c as Single or Married Filing Separate. You can still file your personal tax return as Married Filing Jointly for the year if that status results in a lower tax liability with your W-4 Line 1c showing Single or Married Filing separately. To determine which filing status results in a lower tax liability, you will need to prepare your taxes both as married filing jointly (including both your incomes together) and married filing separately (you each prepare a tax return with only your income).
