I am fairly new, but I wouldn't get either of those damsels. I had them in my tank when I added 2 perculas clowns, both were a little smaller than the clowns, I re-arranged the rock work, and the damsels chased each one around for hours, until the clowns tired down, than the damsels would hit the clowns with their tail fins. I did some research, after my 2 clowns died 1 and 2 days later respectively from the damsels picking at them, and from what I saw, the 3 stripe damsel is not good to mix with clowns, and the yellow tailed is also considered agressive. I returned the damsels to the LFS, who also said the same thing, and now I have 4 green chromis, 2 perculas, 1 flame angel, and a royal gramma, and everything gets along great! I'd recommed the green chromis over the other damsels you mentioned, if you get 3 of them, they will skool, and it's pretty cool to see. I have a 72 gallon and am now thinking of another fish that would be good to put into the tank with what I have. I originally also had a Neon Dottyback, which look nice, but they are pretty agressive, so I took that out too.