Are digital formats of music by major online services like Amazon, iTunes, Google Play typically better than CD quality?

I still occasionally pick up CDs when it is a special edition with cool packaging and extra tracks. I also have a pretty big CD library from back in the day. For some albums that I absolutely love and want to own the best possible version, is the download version generally better than the CD version or pretty much the same? Or does it just vary case-by-case? I'm wondering if there is a superior version that I should be looking for.

Edit: replaced digital with download