It's all about preference. Some people dont like some species because they can become "problem" species.. growing over your other corals. It doesn't mean you should avoid those species, it just means you need to plan their placement more carefully if you want to keep them. I like Xenia and GSP. I don't mind kenya trees and have some of those also. People just need to know what they are getting. There are other soft corals that are hardy and don't spread a lot; get those if you're worried about it.
I hear Xenia are good put near the glass, where they can spread onto the glass and be easier to remove