Currently, all I can provide is an opinion based on a discussion I followed some time ago. And this just got too long for a comment …
If you understand german, here is the extensive discussion on the forum of the german CoC publisher I mentioned above. I don't remember all aspects that were discussed there and currently don't have time to go through that material again to make a writeup here.
If you are just starting with CoC, you might want to start with the 6.0 rules for now. From what I recall, they are simpler and players on conventions will know those, if any.
Concerning backwards compability with older Adventures:
Until 6.0, you had only some skills renamed and minor details like damage points of a gun changed.
In 7.0 you have several new concepts — after testers criticised several of them to break with backwardscompability, it was considered to make them optional, but I am not sure on what the final decision was.
Also, 7.0 wanted to give more power to the players for influencing the story, which might be problematic if the adventure is not flexible enough.
So, when working with existing publications, you will have to pay a bit more attention to the details using 7.0.
With 6.0 you also have a better chance to get help on the web or from experienced players.
Yog-Sothoth.com is very rich source (but concerning the differences between 6.0 and 7.0, all I remember is a flame-war).
Also, I think that compiling a list of differences — without paraphrasing both systems nearly entirely — is only possible by assuming the reader knows the 6th edition.
And it might be less confusing for you to find an Adventure you would like to play (a golden rule is to start with a short and not too mythos-intensive one-shot) — most are written in a way, that allows you to get aquainted with them without thinking aubout the rules. When you have a good grasp of the adventure and thought about how you would present it in terms of atmosphere and descriptions of places and people, you can grab the quick-start-rules of both editions and while reading them think about how that would apply to your adventure.
Thus you might be better able to figure out which edition seems to more naturally fit your style (or what you have in mind for that adventure).
Another possibility is to include your players into making a decision, by trying out both rulesets. This is only feasable if you intend to play on a regular basis.