I guess the easiest way to describe the difference is to say that the Aonach Eagach is higher and longer than Crib Goch. The Aonach Eagach tends to come apart a bit more when you wrestle with it, compared to the cleaner rock of Crib Goch. It's easier to get onto Crib Goch, and rather more difficult to get on and off the Aonach Eagach. On the other hand, if you've already managed Crib Goch, then given good weather, there's no reason why you shouldn't be able to manage the Aonach Eagach. Just expect it to take a bit longer.