Power (equivalent to drive train efficiency) is more important than weight
from
Climbing Power Calculation
70 kg rider 10 kg bike 20% grade 1km climb 200 watts (assuming granny-gear climb for non-elite rider near the end of a marathon race) = 14 minutes 36.6 seconds
take away 500 gm = 14 minutes 30.6 seconds
or
improve efficiency by 2 watts =14 minutes 27.6 seconds
but you are not riding a singlespeed so there is still some sideways chain deflection with 2X and 3X, so
improve efficiency by 1 watt =14 minutes 31.8 seconds
but are you really saving a pound to go 1X since you will need a heavier cassette, a heavier narrow/wide chainring, longer cage rear derailleur
Anyway,
small changes in wattage (from your fitness, tire rolling resistance, drivetrain, aerodynamics etc.) are equivalent to
big changes in weight/mass/grams