I'm constantly working with enormous motorcycle platform files and spending a lot of time waiting. The native files are usually from Solidworks. I'm wondering if there's a benefit to exporting the model as a different file type. For instance, would exporting as a .STL cut down on all the wait time of file importing, laggy response in KS, long render times etc.
I find that loading in STP files go the fastest. Keyshot has to go through a lot of information that it doesn't use when going through SolidWorks models (such as materials, masses, ...)
Parasolids (*.x_t) are a bit more reliable in my experience than STEP.
Also nice is to use the Solidworks plugin, and using that to export to a Keyshot .bip file from Solidworks. Then simply open that from Keyshot.. it feels faster to me, but that could be subjective.
I think STL is mostly used for 3D printing. The ones I've seen imported into KS are always very tessellated and don't look good. Like Kristof, I tend to use STP and sometimes IGES (in the rare event that an STP gives me trouble).