Interesting thread...
I don't know as I would say dislike per se, but the tail type I'm probably least enthused about is double tails -- likely due to the fact that most I have seen have been VTs in cups, where there's so few with nice fin carriage (even a lot of single tail VTs don't have great fin carriage in cups). Then I'd have to say some HMs and Deltas, because sometimes they just look a little funny, especially when they're not carrying their fins well. I absolutely love when a fish has nice fin carriage.
As for color, probably Cambodian. I don't know why...
That said, a nice personality can trump all. My little guy Sharkfin's a real scrapper and I
love it! He had Kostya strutting around and flaring while he flared back with everything he had until I put a piece of paper between them. I joked and said he was like an Irishman (I am, by the way, a large percent Irish). Judging by what fins he has left I don't know as he'd really have caught my eye in full finnage (though I think he'd look amazing as a plakat), but his temperament is just a kick.