As with anything, there are pros and cons. A big pro of Zerene is that it will run on linux. Another is that the author, Rik Littlefield, is a nice guy. Zerene is slow, and I suspect a part of that is that it seems to be written in Java. The people who are exhibiting the very best macro mineral photos all seem to be using Helicon.
Helicon on the other hand only runs on windows. But it is fast. Best of all it will work directly with raw files, which is a huge optimization of my workflow. It does cost more. You pay $200 for a lifetime license, whereas the cost for Zerene is $89 for a personal edition.
Tom's Computer Info / tom@mmto.org