While I disagree with the Prime Rib comparison, which is rather silly, I'm not really sure these two libraries can be compared at all. They serve different purposes, IMO. Intimate strings are very "in your face" with their sound, which can be extremely useful in certain circumstances—particularly when layering.
The shorts have a lot of bite to them, the legatos are smooth, and there seem to be far more articulations that VSL offers. But we're talking a very small ensemble, and while the VSL version is only slightly larger in section size, it has a completely different sound. So it really comes down to what you prefer.
Honestly, the way 8Dio is having bargain basement sales these days, I don't how owning Intimate Strings could be anything but a no-brainer. But everyone's mileage varies.