It's also dependent on what orbit you want. Equatorial is easiest launch to achieve and you gain the biggest advantage from launching east and near the equator

It's also dependent on what orbit you want. Equatorial is easiest launch to achieve and you gain the biggest advantage from launching east and near the equator so it's what was tried first. It's also rather useful if you wish to go to the moon - which is one of the reasons KSC is where it is. Today fibre cables means geostationary is a declining satellite market and a lot of the new business needs to go into much higher inclination orbits to cover a larger part of the earth's surface (think Iridium, GPS etc). For this an equatorial launch still helps but latitude is less of a consideration than the angle you can launch from without hitting any major cities. This is the reason for Edwards AFB, if you want a polar (eg orbit for surveillance satellites) you really don't want to launch due N from KSC - there is a lot of expensive real estate on the eastern seaboard!