Like others have said, it really boils down to the inflight experience you want. F is a small cabin with a maximum of 14 passengers with a nice attendant
assenger ratio, such that you won't have to wait for much of anything. The suites themselves are spacious (I am 6'3" and 190 lbs) and private. My experience - I fly fairly often between LAX and the Middle East - has been good inflight service, with the dining experience really quite good (the mezza in F is outstanding, although I avoid the muhammara, as it inevitably causes me heartburn) and the drinks are top-notch, if that matters to you. Hennessy Paradis is an exquisite after dinner drink, and the Dom is really nice after take-off. While some consider the F class shower/spa, I certainly do not! Nothing is better than a shower, shave and a change into fresh clothes after a 16 hour flight - even if one has changed into EK pajamas immediately upon boarding (I do that because I don't like lounging in street clothes when I can do so comfortably). The F class lounge at DXB has been written about extensively at this site - I frankly find it a bit empty but I've been told that 'privacy is what we want our F class passengers to experience'.
Frankly, I haven't done EK in business class. What I will tell you is that when the attendant opens the curtain for me to go back to the "bar" in J, I walk through a sea of 70 or so passengers with reflections of their video screens in their faces (or asleep). The space isn't bad in any way, but there are just so many people. Again, I don't know if you have any interest in world-class level drinks, but I always have an attendant in tow, with a bottle of the F class drink I really like on EK -- it is Hennessy Paradis, of course. It is pretty exclusive, so the bartender is instructed to put it below the bar, only available to me or other F class passengers.
So, all-in-all, if you are looking for seat pitch and an OK onboard experience, I'd say business class looks OK. If you really want to have an experience flying above the clouds in luxury, I'd to EK F.