In my opinion, the "EX" train are "interim" software. I would say it's to get you to start using the appliance.
The "full-blown" version, with all the additional features, will be released in the future.
To answer your question, you have no choice. "EX1" probably has some bug fixes (public and private) over the first version, EX (or I'd like to call it "EX0").