Although there is no difference at all for just having a Real Estate License, there is a difference if one can qualify as a real estate professional as to the limitations of deductions from rental property due to passive loss rules. Expenses and income are counted identically for all taxpayers.
All residential rental income is considered passive income that can only be offset against passive gains or claimed against other income up to $25,000 per year when modified adjusted gross income is less than $150,000. Unallowed passive losses are carried forward to be used later against passive income or claimed when the property is sold.
For more details see http://www.irs.gov/publications/p925/ar02.html#en_US_2012_publink1000296629
The qualified real estate professional (as defined in tax law) is not limited as to the amount of passive losses that can be deducted in the current year. Material participation in each rental is still required.
"Qualifications. You qualified as a real estate professional for the year if you met both of the following requirements.
More than half of the personal services you performed in all trades or businesses during the tax year were performed in real property trades or businesses in which you materially participated.
You performed more than 750 hours of services during the tax year in real property trades or businesses in which you materially participated. "
So, just having a license is not enough to qualify by itself; but that might, in some cases, help in meeting the qualifications to be able to not apply passive loss rules by qualifying as a real estate professional for both the items described above.
Please ask if you need more discussion or clarification.