Hello! I have an old Macbook (about 3 year old), with the OS X Lion, and I'm planning to get a new Macbook Pro. I know that with time and usage, our computers collects junk files that make it run slower. So, when I get the new Macbook Pro and migrate my time machine back up from the old one, will it also migrate the junk files? What is it best to do in this case? 1. Transfer files manually with an external hard drive to the new Mac?, or 2. Migrate all my backup to the new Mac with time machine? Which one?? Thanks!