If you're going to do log processing, it means you've got data to process. And I haven't worked with AWS since 3 years ago, but in general external bandwidth is

If you're going to do log processing, it means you've got data to process. And I haven't worked with AWS since 3 years ago, but in general external bandwidth is expensive, which is why you want to keep everything in the same data center where bandwidth is free and where you have no latency.