The A900 easily has much better cooling than the CM690. Especially for the hdd cage, which IMO is more important than other components. Also, the construction quality is better.
Cons are - it can get a bit cramped. I have a uAtx board, so its fine, but with an ATX mobo, you'll have to spend a lot of time if you want clean cabling. Also, this does not have a toolfree install. Everything has screws. I guess thats because its designed to be carried over to lan parties, so everything has to be secure.
The full mesh design also creates noise problems, even with the fans at low. Its something you'll have to get used to. But then, the CM690 will not be silent either. As for the dust problem, I've just put in some nylon netting in front of each fan. Should prevent most of the dust from getting in.