I looked at amazon... and was shocked how expensive those things are.
To start with, you should maybe decide for what purpose you want one. e.g for learning "causal+formal" japanese or buisness or specialized on technical issues.
I think you are looking for an "ED" for causal+formal japanese so you must determine if that "ED" has the necessary features which will help you in the progress of learning.
So it should have the foundation of what you want to learn and should easy to use. It does not help you if it has all nice features but it holds you back because it is hard to use.
Meh, many blabla from my side but i fear it does not help much....
Maybe you should ask a teacher what points would be important.
best regards