Hi Sculpy, well there's many different kinds of CAD designers, DWG and DXF formats are only really the most common for people using CAD for 2D drafting like so it replaces a drafting table for making 2D blueprints. There are so many varieties of CAD that the context matters a lot, like you might read in an architectural magazine that the most common formats are DWG and DXF but that means among architects.

re:
> I'm looking to become a designer/Inventor and want the ability to design anything from tiny jewellery findings to jumbo jets <....>

The problem here is that what you're talking about spans a whole lot of different industries, and each industry has its own particular specialized needs and software that is designed to meet those needs.

A Jumbo jet is made up of 6 million different parts and involves a large number of people working together on it. The process that requires is at a fundamental level just nothing at all like the process around doing a tiny jewelry piece.

You don't really want to use the Jumbo jet designing software to do the jewelry piece because it wouldn't be any fun having a fully staffed I.T. division working in your office doing all the database maintenance and TPS reports and what-not while you were just trying to draw some stuff... ;)

For choosing between MoI and SketchUp, I'd say MoI sounds like a better fit for you. SketchUp is very easy to use so it's great for beginners but it's also mainly designed to do boxy architectural shapes and builds everything out of polygons. So if you try to make a sphere for example it's not an exact sphere it will be a bunch of triangles just approximating a sphere. This could indeed come back to bite you if you want to take your model through a manufacturing process later that required accurate geometry. When you build something with CAD solids like in MoI you've got more bases covered as far as different file formats especially relating to manufacturing because you can generate a polygon format output from CAD solids if you need to but it's very difficult to do the reverse.

I can't guarantee that MoI will meet every single one of your future needs but it should be a good place for you to start!

- Michael