죄송합니다 and 미안합니다 is same meaning, but 죄송합니다 is more polite. also 고맙습니다 and 감사합니다 is same but 감사합니다 is made by chinese letter and 고맙습니다 is pure korean word. So to use 고맙습니다 is better i think.

to add to Hyunseung's answer, other forms of the same expressions that you might use with friends/peers/familiars (in decreasing politeness/formality): 죄송합니다 --> 죄송해요 미안합니다 --> 미안하다, 미안해요, 미안해, 미안 고맙습니다 --> 고맙다, 고마워요 정말, 고마워요, 고마워 ((you may see: 고마웡)) 감사합니다 --> 감사해요, 감사해 ((you may also see: 감사, 감사 감사~)) Also as Hyunseung already said 감사합니다 is the sino-Korean expression derived from the Chinese characters "gan xie." Lately there's been an effort to use more pure-Korean expressions like 고맙습니다 when they're available :)