It can go both ways.
If you're willing to shell out a few extra bucks, some bands will prefer the traditional method of recording live string esembles.
However, you can find pretty good string sounds from synths as well.
An example of this is the director for Once Upon a Time in mexico. He scores the music for his own films and uses software based music editors to create his orchestral arrangements.
As to what he uses to do that, couldn't tell ya.