Speaking as a really big fan of all things Anderson, I prefer the CGI Scarlet to the original. In 1967, when Captain Scarlet and the Mysterons was being produced, this was the first series made with very lifelike puppets, with the result that the puppeteers had to adapt their style, as the broad movements appropriate to the older style puppets wasn't appropriate.
The result was that the series could be very static, wheras less acclaimed shows like joe 90 and the Secret Service, made later when the new style had bedded in a bit, are much more watchable now.
In short, the new Captain Scarlet is the really exiting series that was going on in the paintings on the end credits of the original show, or that could be read in TV21.
Many of the old Anderson shows are still superb, though.