More and better test patterns, much better organization, better explainations. The menu navigation of DVE will give you a headache. I think Avia is more usefull overall. I bought DVE for $13 and hoped that would be enough but I found it lacked several test patterns I wanted to use.
For the basics DVE is fine and will help you get set up. If you feel like you need more of anything after DVE, then pick up Avia. I like having both and I'll keep both.
I don't have digital video essentials, but do have the previous version as well as Avia. I also have difficulty navigating through video essentials. Avia is much more user friendly. I myself much prefer avia, but I haven't yet seen the new digital video esssentials so hopefully it's been improved.