If you are looking for the best user experience, then I would recommend staying away from Entourage. It has a nice feature set, but it is poorly written (read: crashes, may cause catastrophic data loss, acts buggy, etc.) and seems focused around enclosing you in the Microsoft experience.
By contrast, Mail has fewer features, is pretty solidly coded, and (along with iCal and AddressBook) is full of hooks that other applications can tap.
If you look around at various cool Mac utilities, you will notice all kinds of hooks into the standard Apple apps (the above, plus iChat, iLife, iWork, and others). This is not because those programmers are pandering to the Mac experience... they just find it incredibly easy to add that functionality because the hooks are already there.
As for the word processor, that is more of a personal choice since you are looking for specific functionality (btw, have you looked at
ScholarWord? No idea if it is useful...) But again, I do find that the Microsoft apps try to lock you into their world. Any other application wouldn't be as restrictive. Also, I do know some people working on their (English) dissertations in Pages. They seem pretty happy with it.