Well, I think it depends on how elegant a function we are talking about. Where I live (northeastern US, large city), for 90% of dressy functions in the winter, a refined pair of boots like #1 would be perfectly fine. I'm talking about most nicer dinners, going to the symphony or opera, Christmas parties, etc. Here, women wear refined boots (or more often, booties, since I think showing some leg looks dressier) even to cocktail parties. Part of this has to do with weather and transportation. A lot of people in my city do not drive so they have to walk or take public transit. However, if the invite is black tie, I'm not sure it's entirely appropriate. For that I would probably wear either dressy sandals (summer) or refined pumps (winter). For the weather issues, some women will change their shoes in the coat room and leave their boots with their coats.
That said, it totally depends on whether you get invited to such functions! I seem to get invited to things like black tie weddings with some regularity.
For the record, I think sandals in the winter looks really strange! (At least here, where there is snow and it gets cold. Somewhere warm or tropical they would be fine.) I would wear closed toe pumps.