"Determination" is a decision. "Determine" is close in meaning to "decide" and can be used in countless ways. "Identification" is a more special word. It means "specify the identity". For example, if a teacher is asked to identify the best pupil in his class, he could say "Tommy is the best". That is identification. If he was already sure that Tommy was the best and didn't need to think, it wouldn't be a decision.