Summary
Same changes as before, but this time, before adding the new content, I'm setting the innerHTML of the target element manually. This seems to bypass jQuery's attempt to remove the existing data, which was the source of the slow down.
Script
Select "File_1", then after it loads, select "File_2". Fastest so far. Now, select "Select File". Again, much better than the previous two. Clicking "jQuery Profiling" to return to the main page, still the same delay.