08-08-2013 02:22 PM - edited 08-08-2013 02:23 PM
Well, as worded, that's actually a tricky question...
The Desktop Software must of course be installed to your PC so as to provide the proper general drivers and such. But the LOADER.EXE method is a little bit quicker (the Desktop Software simply calls LOADER.EXE when you execute, within it, the OS update process).
LOADER.EXE executes in one of two ways. If you have installed (to your PC) a valid BB OS package, then LOADER.EXE uses it. If you do not have a valid BB OS package (and sometimes if you have more than one BB OS package installed to your PC), then LOADER.EXE ignores what may be installed to your PC and instead attempts to connect to the Internet to find what your carrier makes available for your specific device model number. Hence, the manual process of installing valid OS packages to your PC allows you to take complete control and also to use OS packages from other carriers, while the automatic process restricts you to only those released by your carrier.
The key is to be very careful about what is installed to your PC...always the Desktop Software, only one BB OS package at a time, and always removing the VENDOR.XML file(s) each time you install a new BBOS package to your PC.