Everyone of these approaches had merit. They also had strong drawbacks and thus the need to keep trying again every few years. The Rhodes 22 came out with a combination keel centerboard on boat number one in 1970 and continues with this proven system in its latest models. Rhodes resale value is the highest in the industry. Where you sit does the job.
All big boats use external ballast.
In between size boats are best served by a combination. Water ballast, of course, is internal ballast. To get the same effect more weight must be used. More weight means more of the boat under water and more wetted surface or drag. It also means less room inside the boat for you and gear and equipment features.