I really like the Niger trigger, they have a cool crescent moon shaped tail, also the purple color is beautiful. Most Petco's seem to have a Niger, as well as my LFS. My LFS also had a pink tail, huma X 2, and a undulate trigger.
i really haven't seen an ugly trigger. some day, i hope to have a tank that i can keep one in- the only trouble is, i'm a reef addict. every FOWLR i ever owned was only one for a couple weeks, until i bought proper lighting...lol.
I have a niger trigger for the most part he is very calm and minds his buisness but everynow and then he will have small spats of aggression. They do get large but seem to grow fairly slowly from my expiernece.