o my knowledge, there are 2 ways to install dotnet 3.5 SP1
1 easy way, using the command %INST%\dotnetfx35.exe /q /norestart.
And a bit more complicated way by extracting all msi's and creating an administrative install point.
Both are described here.
From a simplicity point of view if prefer the first option, but does it have any disadvantages in comparison with using the command line dotnetfx35.exe /q /norestart ?