1 inch vs 1 1/4 tubing in rad

I could be totally off base here, but I always thought that keeping the coolant in the radiator longer would cool better better than hustling the water through the tubes, thus the smaller tubes should be more efficient. also, there would presumably be more tubes in the radiator since they take up less space.

the argument against I guess would be that; (a) the larger tubes have more surface area for heat dissipation, and (b) the coolant can only flow as much volume as the thermostat will allow, unless its removed or opened up.

like i said, i'm probably out to lunch on this one, but when i replaced my thermostat after running (hot) without one, my crate motor's temp went down 5-10 degrees just by slowing the flow down.