Dragonair will always be the best in the Dratini family. Dragonite on its own is adorable and I really like it, but I can't stand how overweight and sunburned Dragonair becomes when it evolves.
This isn't really an unpopular opinion... I've seen SO MANY people say this. I'm one of them.That's the exact reason why my shiny Dragonair will never evolve. From a beautiful pink to a horrible green isn't a nice transition at all. Wow now that I think about I really don't like Dragonite. It's not a bad Pokemon in terms of stat/design, but in my eyes it will never be as good as it's pre-evolved form.
That being said, I wonder if there is a means to make a competitive Dragonair stand up to the OU Metagame. (Probably not)