Depands what you want to do really. Want to design things that look like cars, planes, etc? Use Moi. Want to design real cars, planes, etc? Then you'll need Catia.

There's more to this than just continuity. Internal and external references along with co-ordinate systems are vital (and required by the industry). Then you're looking at assemblies, again crammed with internal and external references, skeleton parts, etc. And I'm just scratching the surface here.

FWIW: I am a designer at a company that provides parts for major airliner OEM's. Catia is what is used and the only software that can do the job.