Those are considered two of the more "reef safe" fish as far as angels and butterflys go. In my opinion there is no such thing as a 100% reef safe angel or butterfly, but both of those will ignore most corals, but there's always a chance you get one that wants to nip at one coral or another. If you were choosing between the two, I would go with the flame angel first because they tend to be a lot hardier and adapt better to frozen foods.
Hope this helps.