I have been bouncing back and forth between these two gallery programs for years. In my head, not in actual using.
1, 2, 3- True boolean searching of keywords picked up automatically from the IPTC fields.
4 to infinity: The usual: ability to handle multiple media types, fast and responsive with large databases (100K plus) SEO, ease of use, good support forums, customizable design, integration with drupal or joomla or other things, etc, etc.
A few years ago, when I was first looking at the conversion, Gallery was supposed to be way better in most areas, but it did not have true boolean search. Now it does, and I can’t remember why it was supposed to be better. It seems simpler, but also less interesting than Coppermine. Fewer design template options, and I haven’t looked close enough yet to see how difficult customizing the look might be, but Coppermine looks to be relatively straightforward.
All input welcome.
ALSO: Input about **where might be a more effective community to pose this question… **I don’t hang in tech forums, and using the forums for each of the two means generally getting a lot of bias.