If you come along with the solo strings from Opus 2 (which is something I'd be interested in, too, because from the articulation list I think I may need more judging by what I use from Opus 1 full sections...) I'd get Chamber Strings. However, if you have no or little need for small ensembles it will not be of much use for you. Divisi writing and some layering over the full section, but the latter is maybe done better with solo strings (never tested this). You could even go as far as build your own ensembles with solo strings with up- and downpitched versions of the articulations. That involves some fiddling around though [;)]
I suspect if you have use for both packages, you won't regret buying either...
PolarBear