Ezri Dax is best Dax.
Vic Fontaine has to be my least favorite.
I liked him as a character (he showed that the sentience of holograms was a product of advancing tech, and that the Doctor on Voyager was not a special snowflake), and he wasn't too annoying.
But as a concept? Dumb. A holographic councilor might work...if there wasn't a real one right there! Plus, they used him way too much. One episode, maybe, and then the ending like they did. But several? No, especially not at that point in the show, and especially when they are focusing so hard on another cast member.