Both great. I beta tested both. My personal favourite of ALL CO2 content is Westwall. KOAD scenarios are huge - not in length of time (they're mostly around 2 days) but in numbers of units. And obviously Koad builds on maps and scenarios that you already have in a certain form from other modules. So if you like managing that number of forces, on maps you're already familiar with, but in greater detail, then KOAD is for you. Westwall has scenarios that are for me a really nice size (tastes vary on this, obviously), with very beautiful and detailed new maps. Whilst there are a couple of very large scenarios most are medium sized. They are also more dynamic, I think. Or at least there are more dynamic possibilities - whereas with Koad you probably already know the historical set-up which will confine either side to having a tough, tight time at various points, even with 'what-if' variants thrown in. For me some of the most enjoyable scenarios I've played in CO2 are the Dutch scenarios in Westwall. Depends largely in where your interests lie. Tastes vary.