[dnanian]

The source version of the copy was the same, both times. Kernel Panics aren't going to occur in general terms because the copy was 'screwed up', at least not in a way that would resolve itself, so I think something was wrong with your hardware, or a driver, at the time -- and perhaps a power cycle cleared it up. It's hard to say, though, without the actual panic log.

The copy is smaller because, as explained in the "What's going to happen?" section of the UI, we don't copy temporary files, swap files, some caches, etc -- things that have no real meaning across a restart, or are specifically recommended to not copy by Apple.