Both methods, when used by competent professionals, will get the job done without hurting your carpet. Both methods can also be harmful when done by poorly trained or misinformed cleaners. Spend your time evaluating the professionalism, reliability, and trustworthiness of the company who is going to do the work. Ask for credentials and references. Check out the national associations for the carpet cleaning professionals. IICRC.org and ASCR.org. Good luck.