@wpfangirl makes an excellent point. Although I originally assumed that blocks would completely replace custom fields, I now see that they serve very different purposes, and can co-exist.
One area that meta fields shine is that is is easy to display them outside the post’s content, or perform data operations on them: retrieving a single piece of data from another post, or comparing two dates, for instance.
Blocks, on the other hand are for formatting the main content area of a post. If your data only ever needs to be displayed on a single post, then a block might be a good fit.
