I have to agree with you fontadoni, the Apple ones are really good, especially if you keep swapping between different articulations e.g. legato and staccato.
If you write lots of sustained notes/ chords, you can get away with JUST sampled strings. It’s where the melody notes move quickly that samples fall down. I’m lucky here because I play violin and viola so I overdub some real strings and mix them in with the samples – just enough to confuse the listener