I don't really have a favorite tail type. The only betta I've had is a delta tail, but since he's a chronic tail biter he always has a raggedy short tail instead. I think I'll always be more inclined to choose based on the color pattern without really caring about the tail type, though. To be honest, I'm not particularly fond of the doubletail look, but if I saw one that had a really nice color pattern, I would still consider buying it.
Edit: As far as colors, I really like my betta Ivan's color, kind of a metallic blue. I also like red, dark gray (not sure what that's officially called), copper, and multicolors.
Last edited by Moldau; 01-22-2011 at 04:13 PM.