I would very much echo comments by jackiedada above - in particular as regards managing your level of expectations.

Although a long-time fan of Emirates, I am also very conscious that no airline is perfect. In general, service standards in the F & J cabins are good ; but more than once I have come off an EK flight with a feeling that it was all quite 'ordinary' (yes, even F) rather than anything special. In essence I'm talking about the sort of flights which don't give cause for any specific complaint as such, but just leave you feeling somewhat flat in terms of what you've spent in getting yourself from A to B .....!

On any given day, the crew play a big part of course (and, to a certain extent, your fellow pax too !).

If you feel the additional space in F v J is particularly important to you, and the additional cost is not something you will 'miss' or resent once the journey is done with - then, yes, give F class a go. When all said & done, it's really the only sure way to determine whether it's worth the extra money to you - ie in the context of any other personal priorities you may have ....