Ive done this with complete large aircraft so know what you mean by large file sizes.
I found the best formats to use were .xyz and .stl.
After trial and error the scanning company provided both. The xyz format was direct from the scanner (about 250mb) while the stl (8gb) was manipulated (by the scanning company) into a surface body.
My best results were by importing the stl into Meshlab so I could compress it into manageable size. This was because solidworks can only handle a limited amount of surfaces which can be limiting. This could easily lose fine details like what you might encounter.
You could import the xyz direct into SW if you have pro or premium but I didnt any luck or the time to play.
Get the scan company to supply some samples so you can have a play.
Oh yeah - get yourself as much ram as possible!
I work with point clouds on a daily bases. Are you looking to get the point cloud to a solid model or just for checking for interference? Is this a project I can help you with?
Solidworks Pro or Premium will import quite a few different formats, though I have only had direct experience with importing stl surface and xyz point cloud data. Yes you are correct, huge files can be quite unwieldy in Solidworks - it seems to cope quite poorly with large datasets in comparison with other, more specialist packages (Geomagic, Spaceclaim, etc).
If you can get the scanning company to decimate the data before you load it, it will help. With stl surfaces, this will apply a variable mesh that is dependent on curvature, so you shouldn't lose too much detail where it matters. I suppose that if it is possible to decimate the point cloud it would have a similar effect.
The flip-side of this is that processing the data takes time and that costs $$$.
A lot of this functionality is available inside Solidworks, but the fewer points / vertices you import, the easier your life will be getting it in there in the first place! Solidworks starts to chug a bit with very large datasets = reduce the point count any way you can. If the shapes being scanned are geometric, you may consider getting the scanning company to draw geometry (planes and cylinders) through the scan data and omitting the scan points to import? This shouldn't take too much time from their point of view.
Once you have the data inside and manageable, of course you want to use it and this is where Solidworks can be a bit involved. I had best success using the data as a sort of 3D template rather than trying to sketch on the mesh directly. There are other packages out there that work a whole lot better than Solidworks, but I'm with you in spirit (you've already bought the capability to do this, right?). You may also find that the software "loses" the mesh even though it shows it in the feature tree. If you do, I'd be interested in hearing about it - drove me nuts!