I do not know what Flap setting the 777 used, but Flap 25 is a normal flap setting for landing on BA 777s.
Let`s look at some figures:
At a weight of 200T (a typical landing weight), Gear down on a 3 degree glideslope:
Flap 25.........Vref 142 kts........pitch attitude 0.5 degrees....
N1 power..........50.7 %
Flaps 20.......Vref 147 kts............pitch attitude 1.5 degrees....
N1 power...........40.2%
These figures are for a 777-ER Trent 892, using an extra 5 kts of speed (Using Vref 25/20 +10, as opposed to the normal Vref25/20 +5).
The figures are from the Boeing 777 QRH P1.20.12.
What is interesting to note is the difference of only 5 kts between Vref 20 and Vref 25. Also at Flap 20, there is a substantial reduction in drag and hence thrust required. ( N1 thrust 40.2% for F20 as opposed to 50.7% for F25).
The crew would have little or no time to consider these factors with only seconds available to handle a particularly nasty situation. What they did in the time available was commendable. They all walked away, which is the most important thing of all.