My only consideration is that BA use an A380, which will leave you feeling much better at the other end. Personally I don't get along well with 777s, they often leave me with a nosebleed, literally.

That aside, Cathay F is in a different league to BA F. When people say BA F is basically J+, Cathay is one of the airlines they're comparing it to. The space you pay for is much bigger, but the seat itself really isn't much different.