The main and most important difference between SOF and STAR is
that SOF is military and STAR is under police.
It may sound like I'm stating the obvious, but please think
carefully. For many reasons, if police is able to handle, they and
their special unit will handle situation. Else if situations get
out of hand (in SG we may never have a situation that goes out of
hand la i guess, coz we're all too tamed to start riots), military
power will come in hand.
So the roles of SOF and STAR will mostly never cross.