These words are interchangeable, as is pointed out under ample, enough. Each means "adequate," "equal to the required amount": "We have enough food to last us for a week." "We have sufficient money to buy more when we need it." These words should not be used together; "sufficient enough" is a wordy expression. Sufficient is felt to be more refined and elegant than enough, but the words are equally acceptable. Enough, which can be used as a noun, adverb, and adjective, can also be overused as a conversation filler. These are trite phrases: "oddly enough," "strangely enough," "peculiarly enough." If a modifier is needed, then omit the enough. See also curiously enough.
Dictionary of problem words and expressions. Harry Shaw. 1975.