[AdamHeard]

I've got a decent amount of experience with all three (the most with inventor), and from the perspective of someone trying to design something with many parts, then manufacturing it, I would say I prefer SolidWorks the most.

It's just the easiest and most intuitive to use, it also has a totally subjective more modern feel. I believe it's interface for sketches is far superior.

As for Pro/E having CAM as an advantage, there are similar options for solidworks (no idea for inventor).