Drupal 7 or Drupal 8?

Every time there is a new version of Drupal out, the question of using the new version became the frequent one in most of the meetings with client. Deciding to use or upgrade the new version comes down to your project and what modules it needs or currently has. As in upgrading, the process of keeping your old content might bring some extra challenges.
Considering the open source ecosystem of Drupal, you might need to give the new version a bit more time to mature and be ready for your project. Nevertheless core modules of newer versions would be much more mature than old ones which might speed up this concern.
At the end of the day your project developer is the best person to check and test new version and available modules to make the decision if the new version of Drupal is ready for your project, or you need to give it a few more months. You might consider to giving back to Drupal community by providing some sponsored module development to speed up the challenge of having new version ready for everyone.