As you know, the Dimension Violins are not recorded as individual solo violins, they are recorded as a section, performing all violins together, but each instrument microphoned individually. Therefor there is a kind of bleeding between the instruments, which is most obvious with samples which are not static on one pitch like the portamenti. If you compare the individual players you will recognize that the portamento speed is slightly different for each player, a simply matter of personality and how the the players are used to perform their portamento.
Performing at least two players at the same time this kind of bleeding effect will dissapear even if the two players perform a portamento on different keys.
That's the most important difference to our dedicated solo string library, and therefor Dimension Strings are simply not promoted or recommended as a replacement of our solo string product.
As usual everything is also a matter of taste and depends on a lot of factors. To make a simple example: I wouldn't try to perform a Bach solo partita with a Dimension Violin, on the other hand I guess that the Felix Mendelssohn Bartholdy String Octett Opus 20 would work quite well.
best
Herb