I pick my fish based on personality and whether or not they "call" to me--sounds silly, but I have owned each variety over the years, and I have loved each fish for what they are. In my experience, my simple veil tails have had some of the most intelligence and most outgoing personalities, but were most vulnerable to tail biting. Crowntails I had were beautiful, especially in their movement, but over time their rays tend to break. Halfmoons are gorgeous, but tend to be less active. Plakats are very active, but don't have the same effect as the longfins when they move. I love their aggression level and chunky manly bodies, though. DBTs have kind of an odd shape in my opinion, I love the fullness of them but there's something a little off with their topline, and they seem prone to SBD problems.
Even after going over all that I still can't pick a favorite, lol.