both setups have the same wheel size (24x1.75)
both setups use the same crank length (180mm)
both setups use the same size chain (3/32)
setup #1 42T front, 18T rear (56)
setup #2 28T front, 12T rear (56)
The variables I see are:
setup #1 The links of the chain will bend at a smaller angle around the larger gears, the chain has more contact with the gears, the gears and chain are bigger(heavier)
setup #2 the links of the chain have to bend at a bigger angle, Does this effect the performance of the chain? Does it require more force to rotate the chain? There is more pressure on the individual teeth of the gears. Does this affect the performance of the chain? Does the smaller rear gear affect acceleration?
Are there other variables I'm missing? Will it really make a noticeable difference to performance?