I don't think any angel is completely reef safe, having said that I have one in my SPS tank and it doesn't nip at any of my corals. Sometimes you get lucky.
Of the dwarf angels, they're probably your best bet, but like mentioned every fish is different. Depending on the size of your tank you may want to look into something from the Genicanthus family. It would be extremely rare for one of them to eat coral.
-Justin