Not really, these numbers measure different things and are both important as they are defined today. disk.indices is a good measure of the size of the overall dataset and is insensitive to things like hard-linking, whereas disk.used tells us how much real disk space we're actually using right now, accounting for hard-linked files, filesystem overhead (e.g. rounding up small files to a whole block), non-file space usage (e.g. directory entries), and other data also stored on the same filesystem.
The docs do spell out the difference.