Hi
Yes it's true often people only compare a bare Joomla with a bare Drupal. Seblod is not know enough! This is why at Pulsar we regulary try to push the seblod solution in events. We are convinced that the more we are , the easier it will be to get a better solution.
I really like seblod which is according to me a very good way to extend joomla but the main problem, if you want to compare it with Drupal, is the joomla/seblod frontier, not the cck itself.
We have big issues with the way joomla builds its routes with itemids for example. Joomla router is based on menuitems and it only knows the core joomla menu types (articles, list of articles of a category, blog...) but unfortunately not seblod list menu items.
The category depedency is another real issue since Joomla will try to guess the proper sef route given the category of the content. but now we have tags, seblod lists etc... which are not taken into account in the router.
There are other examples like this one. It shows some difficult issues not with Seblod... but with the CMS/CCK frontier.
cyril