I've used all 3. Foxtrot (and again, this is the Pro version), just works and is powerful. It's also crazy fast. The only caveat for me is that it doesn't seem to do so well with emails (I have 85K emails). For this reason I have Devonthink Pro. However, Devonthink is slow in opening and if I were using it constantly, there are too many beachballs. A tremendous positive with Devonthink is if you also want you data on iOS. You can do this with Foxtrot, but it's not so elegant. DevonSPHERE left me all meh.