I believe only the Elite version is available as a demo download. It has several features that are indispensable to me, including Clearview Plus, PRIME noise reduction, the ability to create custom palettes and the anti moire tool, among others. The Essential version does not contain Clearview which is a major feature to my mind. PRIME noise reduction is probably the best and easiest to use noise reduction tool made by anyone, and the results are almost magical with the elimination of almost all noise with relatively few artifacts, if any, even when set close to maximum. It too is not available in the Essential version. The ability to create custom palettes allows you to make the interface your own, but custom palettes are also not available in the Essential version. Additionally, custom palettes allow you to eliminate the duplicate copies of some tools which appear in several of the built in palettes.
Obviously some people prefer the Essential version for its lower cost, but for me it would mean giving up too much. I also have DXO Viewpoint 3 and and DXO Film Pack 5 which are two standalone apps that also integrate into PhotoLab. I personally would not want to do without them as well but their inclusion with the Elite edition of PhotoLab does make the entire package fairly pricey.
Here is the list of all the differences between the Elite and Essential versions of PhotoLab. Click on the image to enlarge.
The following images are of my custom interface which could not be accomplished in the Essential version. I have created 4 custom palettes in place of the standard ones which allows me to move and reorder tools as I wish.
Mark