Pic_Index gets my vote. It is very flexible and easy to use, where I find all the options of WebGen2 confusing.
However that may come because I find no reason to explore it as Pic_Index does such a fine job.
In fact I now used it to present my business in a slideshow in my site. It took just a tiny little editing to nest the directories.
Take a look at [link]
It is in Dutch but it will give an impression.
It was done with an Artworks-template and although Artworks kan export jpegs directly I used OHP to export because size and compression can easily be set there and it does it in one go.