No one joint compound is perfect for all tasks. In fact, every compound has its advantages and disadvantages and you need to select the specific elements that are most important for the job at hand.
The basic problem is that when you make a compound more sandable and easier to spread that compound has less strength. If you need a stronger compound, it is harder to work with.
Here you will find a through discussion of all the basic types of drywall compound -- even regional differences found across the country.