I always use "2 - Triangles" for surface export. That way you'll be writing the definition of the surface (triangles) as you see them in TBC. Importing applications should be using the exact same definition as well so it theory there should not be any discrepancies. This should have maximum compatibility.
If you export the SourceData, that is with option "1 - Points and Breaklines" or "1 &2" or possibly with "Optimize for data", you run the risk of the importing application deciding that it will rebuild the surface and possibly end up with a different result. This even happens with TBC (getting a different result when rebuilding from source data that it exported). Occasionally you might want the importing application to rebuild the surface, but unless you know that you need to export that data I would omit it. Some applications only accept the Definition for a surface, so if you use "1 - Points and Breaklines" for your export (which omits the Definition), those applications reading your file won't import anything at all.
This has been my experience anyway.
Andrew