My experience with 3rd party vs. Canon batteries is:
  • 3rd party perform well for number of photos, but they don't hold a charge as long as canon. I'm always charging the 3rd party batteries the night before an event.
  • I've never had a 3rd party battery leak, but I read reviews of products before buying to try and avoid such problems.
  • Canon batteries hold the charge better when stored in the camera bag,so I use them asthe backup.