I'm with everyone else here on the 6 prongs for 2+ carats... even for 1+ honestly. That story about the diamond falling out - horror! You could definitely lose one prong out of six and the diamond would be totally safe.
I have the Tiffany classic and to me that's just the most gorgeous setting, BUT they really do have subtle prongs - a well made 6 prong shouldn't smother the diamond at all. Then again I was in Cartier yesterday and their 4 prong settings TOOK MY BREATH away! Seriously so beautiful and kind of squared-off looking ... you cannot go wrong though!!