Treasure-Diver-
I can not give a comparison as I have never used a EXII. However I just wanted to say that as a relative noob (been doing it about 3 mo.) I have gotten a handles on the SignaGraph feature of the DFX. My finds thus far have been spot-on to the signagraph identification of the machine, and simple enough that I could pick up on it right away.
That feature alone really makes the machine worth while to me. If you have a dealer near you I would go and ask the salesperson to show you this feature, as well as corresponding features on other machines you are thinking about and go from there.