I have read a lot of arguments here, most if not all of them are valid taken from both sides of the issue.
Which leaves us with the only one that matters.. FFG decided on the release order and that is that.
I for one will be happy to get my hands on both of them.
However there is a reason why I would have liked to see the Battlefleet book come out first.
As I see it the Edge book will be purely additive to my campaign. That is I should be able to use all of the information in it regardless of what I have created to fill the empty spaces of Koronus. All the systems and planets I have detailed can just be stuck in there with little or no trouble. Thus all the work I did making it will not go to waste and I get full value from the book.
The Battlefleet book on the other hand will not end up being purely additive. All the time and effort I put into creating house rules (for combat, ships, components, order of battle and history of the battlefleet, etc) will either be wasted as it is replaced by the information in the book. Or I will keep my house rules and thus not get full value from the book, as parts of it are no use to me. The longer I have to wait for the Battlefleet book to come out the more house rules/info I have to create.
Thus I would like the Battlefleet book out as soon as possible.