[grim]

Just to be clear, Inventor was designed by ex-ProE programmers who wished to create a program that was easier to use than Pro and still did what they want.

Inventor was also created to be flexible in design and NOT be limited to having to constrain absolutely everything to a reference or define every dimension on a sketch. That type of constraint can interfere with the design process when you don't know exactly what it is you wish to define or wish to create an adaptive design.

It is just two ways to approach CAD design. Think ProE as more structered, Inventor as less structured. They are both good packages.