As an engineer, I assume that if I keep the conduits to the NEC minimum size, that the wires can be installed with undue trouble. However, as the contractor and bidder, I think you are free to upsize the conduits however you see fit if you think it will save enough labor to make a difference.
I like to give the contractors some freedom to do the most efficient installation possible. Contractor A may install it as we show it, Contractor B may upsize the conduit a notch, and Bob likes to downsize the conduits.