This week's book giveaway is in the Mac OS forum. We're giving away four copies of a choice of "Take Control of Upgrading to Yosemite" or "Take Control of Automating Your Mac" and have Joe Kissell on-line! See this thread for details.
The project interchange format includes a bunch of files that make up the project. The only time I've used it was to send a project to IBM for troubleshooting. I would say to try it both ways and compare if you have some reason this matters. You can import the file into a new workspace to see what comes out.