I think one of the best places to start Nikyvee is to visit Corels site and compare the features of each and I think you will see that there is a lot of difference between the two.
I have both programmes and I am constantly finding that there is a vastly more choice and control over the workspace and the tools in CPX. That is not to diminish CE4's fantastic capabilities, which is a superb programme and although it is aimed at the hobbyist and is even child friendly, it is capable of producing some very professional results as you get to learn how to switch between the different tools and adjust them.
I think Painter Essentials 4 is great for the photographer who wants to do something more artistic with their photographs. As its name suggests it has all the essential tools and workspaces required.
However I feel that the full blown Painter is aimed more towards the professional end of the market as well as towards the person who would like a more traditional feel to painting on a canvas so is perhaps more aimed at the artist rather than the photographer.
Having said that there are many photographers who are turning out fantastic painted art, so far removed from the original photograph that they end up with two distinct forms of art.
There is far more choice in the work space and the tools in Painter X and you can take full advatage of working with layers and masks. Not only is there tremendous control over the way the brushes work but there is also the capacity to create your own brushes, papers and patterns and share them with other people.
Due to the complexity of the abilities of the full blown version I found it hard to find my way around CPX, but I think that this was because I was not familiar with graphics programmes at all, and did not really understand what any of the terminology meant. Essentials did not create this problem for me and it was much easier to find my way around. In fact by sy studying the way its much more user friendly interface worked I was able to start to unravel some of Painter X's tools and workspace. This in turn gave me ideas as to how to stretch the capacity of Essentials 4.
Now with the help of Corels training partner ... The Digital Art Acadamy .... I am learning how to produce artwork that I never though myself capable of.
I hope this goes some way to answering your question Nikyvee. I am not able to go into the technical specs of the differences but just share my own experience of it. I think Essentials 4 is a fantastic way to enter the world of digital art.
If you want to experience the difference yourself once you have a grip of the programmes you just bought, then I suggest you try the 30day free trial version and if you take it along with one of the wonderful beginner/intermediate courses at the acadamy (also 30days) I don't think you would be disappointed.