We took an initial performance hit as a result of not moving everything to Ohio at once. We moved our EC2 machines first but then saw increased latency between other services like ECR (where we store our Docker images) and Kinesis Firehose that were still in Virginia, so ultimately we moved those too.
So it wasn't so much that Ohio has worse performance, but that talking to services across region does.
One note on Firehose specifically for the curious - we make requests to Firehose in Ohio, and then Firehose sends the data to S3 back in Virginia (which we didn't want to move). Normally sending data across regions is expensive, but Firehose actually absorbs the cost in sending the streams to S3. We're honestly not quite sure why, but it worked out great for our costs!
So it wasn't so much that Ohio has worse performance, but that talking to services across region does.
One note on Firehose specifically for the curious - we make requests to Firehose in Ohio, and then Firehose sends the data to S3 back in Virginia (which we didn't want to move). Normally sending data across regions is expensive, but Firehose actually absorbs the cost in sending the streams to S3. We're honestly not quite sure why, but it worked out great for our costs!