If you'll carefully select a right DAM solution that will not damage your existing metadata while updating your images (as RedGrittyBrick said) you will have more benefits with saving your metadata to images:
- You can easily recover all your image descriptions (and hundreds of hours of your hard work) from metadata in case of your database failure. Just answer to a question: whether you are ready to start annotate your image collection again.
- You can embed your copyrights to images so others can not illegally them
- You are not tight with your DAM solution and can easily migrate to another DAM solution later. So at least consider to using a DAM solution that allows you to store metadata in images if you'll need it at some day.
- You can exchange information between two applications on the metadata level: for example use Publishing, Editing and your DAM tool.
Of course, the above said is true if your DAM solution is a mature product with a proven track of customers, and your metadata will be correctly written into the images according to XMP/MWG specification.
And of course you need to backup your image originals and arrange an automatic, daily backups of your database.
Avoid DAM solutions with the following issues:
- Limited support of metadata standards. Random support for XMP or Native Format Specific metadata.
- Incorrectly written metadata that can’t be read in the same way it was written. For example, very few products can save/read correctly hierarchical keywords and split the location into Region\Country\State\City\Location according to IPTC\XMP\MWG specifications.
- Limited succes in writing metadata for various formats, including Camera RAW, PNG or PDF.