what is the difference between "감사합니다" and "고마워요"?

My 2 cents,
Both are the same in meaning, but "감사합니다" is more formal than "고마워요", and the term "감사" is a sino-Korean word while "고맙다" is a native Korean one.^^/


\^o^/

Bascially, they are same.  You can choose one of them to use it . ;-) 

감사합니다 could be more polite way to express your gratitue to someone than 고마워요.  

You can use both for someone who is older than you.   

Hope this helped !