Visual Portfolio (free) builds galleries from posts and Media Library images with five layouts, four skins, a lightbox, filter, sort and pagination, plus the Project post type and the Portfolio page.
Pro adds social feeds, taxonomy galleries, albums, local video items, hover media, proofing, watermarks, password and age gates, right-click protection, advanced click actions, Quick View, deep linking, search, image filters, typography and dimension controls, the Caption Move skin, AJAX cache, custom breakpoints and white label. Pro contains the free plugin, so you never run both to get everything.
The full comparison is at visualportfolio.com/free-vs-pro.