If you wan a true appraisal of a property you should hire an appraiser.
Yes they both have access to mls, and both can give comps.
NO - they both DO NOT have equal training.
Realtors, or Agents, are licensed to SELL real estate. Appraisers are licensed to APPRAISE real estate.
Major difference between the two types of licenses and training -
To obtain a real estate sales license one must be a US Citizen or legally able to work in the US, be at least 18 years of age, minimum education of High School Diploma or GED, complete the required 90 hours real estate classes (usually 6 weeks), pass the required State exam, pay the appropriate fees, and have a Broker to be affiliated with (hang their license).
To obtain a real estate appraisal license one must be a US Citizen or legally able to work in the US, minimum age 18 years, minimum educational requirement of an Associates Degree, complete the required 150 hours appraisal/USPAP classes (usually 8 weeks), complete 2,000 hours of supervised training in a minimum of 18 months or longer, submit training logs and sample reports (chosen by the State Board) for Board approval and permission to take the State Exam, pass the required State exam, pay the appropriate fees.
Agents provide an estimated selling or purchase "PRICE" - Appriasers provide an estimated market or appraised "VALUE".