Recently flew SQ F for the first time from SIN-LHR on the 777, and if paying with miles, IMO I don't really think it's fair to compare the A380 to it, as you can always get seats for the 777 at the saver rate when the booking window opens up, while the A380 (at least on this route) is always at the advantage rate.

Is the A380 better? Undoubtedly, but you're also paying an extra 84,000 miles per person, which is 59% more, quite significant.

However, if one is paying with cash then I guess it would be a no brainer to choose the A380 (unless there's also a difference in the cash cost? I wouldn't know)