Best reef/best dive? Impossible question: depends on what you like. Shallow/deep, lingering or ripping current, etc.
My take: I'll second sharky60 above - I did a continuous 2 hour dive on Columbia Shallows (the shallow depth makes this possible), and I'll never forge that dive for the beauty and variety of the ecosystem (Thanks, by the way, to Jeremy at Living Underwater for accompanying me the entire time!). One the other hand, we hit Barracuda once when the DM estimated the current at 5-6 knots, and WOW, that's what I call a 'star wars' dive cuz everything's wizzin' by. Barracuda was in great shape and had lots of nifty pockets that you could duck into to escape the current. Thanks, by the way, to Aldora for that dive.
-Al