Following on from the thoughts of Madmaximus and Fascination, for me, whether the man wears a Suit or Tails depends on what the woman is wearing and how their respective costuming choices look as a “couple.” If the man is wearing Tails and the woman is in a more traditional formal gown, that look works for me – both going for the ultimate in formality. But if one of them opts for a less formal look, then the other should match it. So, if the woman is in a gown with lots of cut-outs and slits and skin, I then would prefer to see the man in a Suit. Tails in that instance would appear mismatched in formality to me. If the man wants to wear a Suit, then I prefer that the woman wear a less traditional gown. More formal, less formal – I’m open to either as long as it’s a “matched” look as a couple.