Dave, I don't have benchmarks I can publish for this. My rules of thumb are: if you need bandwidth use the local drives striped. If you need I/O ops (i.e. random access) use EBS but watch the cost. You can stripe across a couple of EBS volumes and I know of people who do that, but I'd work really hard at somehow splitting up the load to avoid it, it just seems like pushing the envelope too far.