First priority for me would be location of departure and schedule.
Then I would look at onboard product next (lounge provision is largely irrelevant for me, since you will spend far more time onboard than in a lounge). Therefore 777 trumps 747 for an overnight flight in BA F - the 747 F product is cramped (I do chuckle that some people clamor so much to get 1A on a 747!), in my opinion, and 777 gives the feeling of more space.
IFE is not really a consideration since an overnight for me is all about sleep, sleep and sleep (granted, the 194 does leave very early to really get your head down from take-off). If I was needing IFE on either of these aircraft, I can improvise with my Netflix account which is always refreshed and significantly better resolution.
Lounges, as I said, nothing to get excited about.