My preference would be for EU4, just because I like EU4 better and I spend a bit more time in that AAR world than I do in CK2 sadly. Although my opinion shouldn't matter. It's yours.
I just like Denmark in EU4 because she was a great power for much of that timeframe, but this gets lost. So much potential. Of course, I like to play a "historical yet a-historical" Denmark when I play. Denmark-Norway, keep Scania, but allow Sweden to eventually go free so I'm always threatened by an anti-Danish Swedish alliance, while I'm also off colonizing parts of the Americas and Africa! (I just get bored with the blobbing, I find more enjoyment by keeping a certain balance of power to keep my interest in my games since I have a bad habit of becoming bored if I get too powerful.
)
Of course, this is a truism.
Your AAR. Your game. Do what you will be happy with. Not potential readers. Readers will always read. Sure, we like to have some enjoyment too, finding new ideas, see how others play the game, get involved into whatever story you're creating. And that's the key. In an AAR, you're telling a story. Whether it's a story in gameplay, narrative, gameplay-narrative mix, or history. It's all about the story. Whenever you post, your readers will read. What is that saying,
build it and they will come? Publish it and they will read.
So whichever one, CK2 or EU4, you think you produce a better story for, be happy with that story and product, that's what you should do. Nothing ends an AAR more than a detached author!
Because in the end, you should be happy and satisfied with your work. (Plus, with my affinity for history AARs, Eu4 has more beautiful paintings and historical images to use.)
Good luck.
Cheers!
