For solo string music you should not use Dimension Strings. They are not designed for solo use, but rather for orchestra with divisi, layering with other ensembles for added complexity, and alone for smaller orchestras. If you use them for solo it will be a slight distortion of the effect, because there is sound from the other 8 players audible on each individual instrument. It is the same thing with Dimension Brass - you would never use them for a brass quintet for example, because you can never hear the tuba without a little of the bass trombone, etc. The whole idea of Dimension is for ensemble, not solo use.
For solo string music you should use the Solo Strings exclusively.
However, the Solo Strings blend extremely well with Dimension Strings, creating an even more complex sound for orchestral. In general, I've noticed how the Dimension Strings act almost as "glue" for putting together the other string libraries into new orchestral combinations.