Well, it all depends on what those Ws stand for. For instance, if that is a Water Sylph as opposed to a Wind Sylph, you should definitely focus on that one. The Wind one is still pretty good, but Water is OP. Same with the Death Knights, the Water (which I have) sort of sucks balls unless they fix its "can't die" skill, but the Wind one has that awsome rez. And the Fire one by itself is worth having. And the Pierrets, I get fucking raped occasionally by the Water one, but no real idea on the Wind one.
So depending upon which ones you have, you could have an awesome set of creatures, or a pretty good set.