With laptops with on-site factory warranty, you can be sure you'll have a properly working laptop. If you have technical problems, someone from the manufacturer's office will come by and solve the technical problems with your laptop. That's useful if you depend on your (business) laptop, for example because you're self-employed. On-site factory warranty is different from carry-in warranty. The latter requires you to send the laptop if something is wrong. This way, you can go to the office or a work trip without having to worry.