If you are unsure of experience you can always inquire as to if they have dealt with your situation in the past.
An Enrolled Agent is someone that has gone through a lot to be a tax professional because they have passed background tests and tax tests that were given by the IRS. These agents are known for dealing with complex tax situations and they can represent you if you should go before the IRS for an audit.
CPAs or Certified Public Accountants are accountants that have passed the CPA exam and they have licensed by the state that they work in. These accountants have specific areas that they specialize in as it refers to accounting. Some CPAs specialize in tax accounting while others specialize in handling tax issues. CPAs can represent you if you need to go in front of the IRS because of collections or an audit.
A tax lawyer specializes in tax law. They have gone through years of schooling and have received their masters of law degree in taxation. These are the attorneys that you want to use if you have a difficult legal matter like if you should take your case before the US Tax Court or you should prepare a return for an estate.