Transferring files to a new PC can be more complex than it would seem. On a Windows PC, there are files scattered about that are tedious to find and move to the new PC, so using a service or software to do so is probably the easiest way unless you are a computer hobbiest. For instance, the most typical files to move are the ones in the "My Documents" directory and each user ID on the PC will have their own My Documents directory. Beyond this location, there is downloads, desktop, pictures, music, and video folders. If you want to preserve your browser settings, you'll need to back it up too. The FireFox browser makes this relatively easy, but I'm not sure about others. Thinking beyond moving files, there's also all of the installed apps that need to be restored. To summarize, changing computers or the local storage drive is a complex endeavor, so hiring a service or software to migrate to the new PC is probably best.
Regarding the comments on iOS (Apple), Windows, and Linux, as a user of all three OSs (Operating Systems), iOS tends to be the most user friendly in my option. Giving my parents iOS devices has reduced my tech support duties and their frustration. If one backs up their iOS to iCloud, it's relatively easy to migrate to a new PC or device.