Don`t get me wrong I`m not saying there`s anything wrong with the 777, it`s just Fugginungly. On the inside great cockpit <way better than the -400> Heaps of go. Never runs out of tank space etc..
And remember what your mother said
`It`s not what you look like on the outside that matters, it`s what`s inside that counts. So you go back out there, and ignore those children throwing rocks at you Johnny`
On a more serious note, I am loath to try and explain it, as I will spell sumfing rong and some techy will crucify me. <however if I say it quietly they may not hear... it has to do with the amount of time spent in cruize and induced drag. On a long haul where most time is spent in cruize, it is beneficial in fuel saving. Short haul, not so helpful. I fly something else that has winglets, and last time I taxied into something and knocked one off, we had a fuel penalty of 3%. Another answer may be that the 777`s wing was totally computer designed, and just has amazing aerodynaimcs.Now some may say `But the 777 can go long haul as well, so why no winglets?` To this one must reply...
`It`s just too fugginugly`