If it IS only 3 years, you're probably are better off going for FD. Shorter training as you're all ready typed, you'll stay current Command which will be important when you leave, if you live cheap you'll probably be able to save- not so much if you are an F/O in company accomodation in EK- AND if you go to EK you might get put on the Airbus, which is a TERRIBLE lifestyle.
If you think it MIGHT be a loger term thing, it''s a harder choice that might come out in favour of EK (though, bear in mind, times to upgrade are bound to increase).
Good luck!