like I've said before, everything depends on what we are really looking for.
One user's trash is another user's treasure

F.e., DeepBassNine is a very rare tracker, but why on earth we need it, if we like other kinds of music that those present there?
Art Of Misdirection is another rarest tracker, but how many people are really interested in magic tricks?

So, choosing the trackers you need, it's totaly up to your own interests.