Sometimes. The more expensive varieties of EBS provide comparable latency numbers to local SSDs (by using fancy on-hypervisor volatile storage or something? No idea), for an added cost.

A separate set of behavior exists for RDS Aurora, which isn't using EBS underneath, so it might be worth looking into the Aurora latency characteristics (vs. cost, of course; Aurora ain't cheap) if you're concerned about the performance impact of EBS-vs-local-disk.