Originally Posted by jsaronson
lead will give you a lower center of gravity than a cast keel of the same size. Alos, no corrosion issues. Lead is WAY more expensive!
On modern keels that is not very meaningful. They are made of steel for the foil and iron or lead for the bulb. The difference on the CG is not significant. What is significant is the size of the bulb and the associated drag.
Considering the same boat the one with a lead bulb will be slightly faster than the one with a iron bulb but the difference is much lesser regarding the time where the keels where all cast Iron or cast lead. There you would be right regarding the considerably lower CG on a lead keel. To compensate that the Iron keel would not only be bigger (more volume) but also heavier.
That would count negatively on the boat performance on two counts: Drag and weight.