IMHO frozen CBW is better value for money compared to frozen blood worms. Frozen blood worms contain a lot of water. Whereas the FCBW are solid worms.
Not quite sure about the nutritional values of both. It's best to feed a variety of foods. I feed mine flake, beef hart (home made) freeze dried and frozen CBW and blood worms.
As an occational treat they get some live food like white worms and red crawlers.