Based on it’s history, OpenCSW is a project that was made by forking blastwave repository. Both project offers very nice package management similar to apt-get debian. it’s a difficult decision to which which one you preferred especially if you have a lot of solaris servers.
when the project begin splitting 2 years ago, both repos seems similar. however, by the time goes, i think they show more differences, and incompatible each other.
For me, I prefer to use OpenCSW because they provide the packages i need compare to blastwave. i need nginx packages and i found it in OpenCSW.