Stan:
TE flap positions 1-15 provide increased lift;positions 15-40 provide increased lift and drag. (FCOM 9.20.17)
Just get out of the plane and look at the way the flaps extend...
The 10% fuel burn for flaps 1 it's about holding...holding at a lower than clean speed....
Using landing gear for increased drag and using it to increase ROD can be diferent.
First case,you need to reduce speed,so at 250-260 kts you select gear down...very noisy ,and a lot of discomfort.
Second case,you descent at 210 kts,speedbrakes up,and you need anti-ice-so higher thrust....this will decrease you ROD,to increase it you can select gear down.....not do noisy or dscomfort due to already lower speed.
...
Brgds