Synth strings can be great, but in their own aesthetics. I'd argue the sample pack is much, much more realistic and rich sounding than any synth patch you can come up with. There's no easily programmable synth that can emulate the mixture of a dozen or so strings vibrating at slightly different pitches. Creating a single, somewhat realistic violin is almost impossible outside of very large physical models (there's a good model in Reaktor by Chet Singer). Even dedicated physical modelling synths fail at that task.