It's much safer to install from your computer rather than over the internet. Package losses or other interuptions, etc. having the installer waiting whilst it's receiving data is hazardous. Also some data may be corrupted due to over zealous firewalls or antivirus, etc. So using the Offline installer ensures a safe installation because all the data is within the installer itself. Commonly people's installations are corrupt due to using the online installer. This also applies to LW.