Dean,

I don't think hydrostatic pressure works that way. For instance, it doesn't matter whether Canyon Lake Dam has 1 foot of water 100 feet deep behind it, or 10,000 acres of water 100 feet deep behind it - water doesn't compress, so the hydrostatic pressure (head pressure) is the same.

Math tells you that 1" will support almost twice the flow as 3/4". That being said, where ever there is a restriction, it will slow it down. But my motto is: Bigger is better.