Hi Burr,

> I'll be designing actual parts and things like assemblies,
> but i wont be designing buildings. Interoperabilty is a key factor.

Well there's a key word that points to Solidworks, "assemblies".

This is where Solidworks has it's strengths over Rhino, for example in Solidworks when you do an assembly you have the parts 'mated' and these mated faces are remembered by the software so if you move a face in one part say by making it slightly thicker, the mated part would automatically adjust to it, or if you have a shaft diameter linked to a hole diameter in another part, when you change the hole diameter the shaft will adjust accordingly, this is what parametrically linked is.
But Solidworks is mainly a solid modeler the surface toolset is not as rich as Rhino's, like it would be more difficult to achieve more organic shapes in Solidworks than it would in Rhino or MoI.

So you have to weigh up the strengths and weaknesses of each software with what you want to use it for.

Hope this helps.