When determining filing status, you should consider any and all relevant factors - not just the size of the refund. Unless you are married or have children, you are generally required to use only one specific filing status option.
Head of Household is usually better than Single or Married Filing Separately.
Single is usually better than Married Filing Separately.
Married Filing Separately usually results in the smallest refund or most amount of tax to pay to the IRS.
If you're not sure of your filing status, you can choose, I'm not sure - help me decide on the Filing Status screen and we'll help you figure it out. Or you can use the IRS What is my filing status? interactive assistant instead.