Picking up favorite desktop search is depending on you tasks expected from these desktop search software. As for me, email search is *MUST HAVE* task, file search is a plus but not have.
I finally picked up X1, after I tried copernic, WDS, GDS and others.
Copernic is the best in interface I think, it can break results into several categories, and it's beautiful. but as I said in early, its email search is just entry level. It can search, but gives you less capabilities to deal with searched items. For example, if you want to delete all the searched result, you have to do it one by one.
WDS is better in email handling, but it's tooooo slow. It slow down every things in my computer, I have to give it up.
GDS, oh, how I can say about it. It doesn't give you the opinion to choice folders in my outlook. I have 2000+ emails in delete folder, GDS just continue to index it without asking.
X1 is not as beauty as others in terms of interface, but it did get job done. In terms of email search, it's far better than any other desktop search application.
Except email search, I really don't think desktop search software is useful. If you want to locate a files, locate is good enough.