I think Michael Dorn said it best. Something like...he had the most fun on TNG (clearly they enjoyed goofing off on-set), but he is most proud of his work on DS9 (a more serious set, but arguably the better series for character development).
And you can see that when you watch the character side by side in both series.
I think Ezri, given one season, becomes a very rounded character and is honestly one of my favorites. When we talked about Jadzia on Literary Treks, we talked about how she is able to help those around her find themselves because of her many life times. Ezri is able to do that for Worf, as we have mentioned here and that is a big accomplishment for a character of only one season.