I think they are almost same. 개 : change 과 : fault, bad things 천 : mend, move 선 : good *in our dictionary, it means, 'mend one´s ways' 환 : change 골 : bone 탈 : take steal 태 : be pregnant oh you need to know the origin of this words. * turn over a new leaf usually, we say '개과천선' for personality and '환골탈태' appearance. just 'USUALLY' you can choose anything.

They are same in meaning.:) \^o^/