We're planning to add a way to compare any two tests using the SpeedCurve UI.
In the meantime here's a quick hack you can use to compare any two tests using the Deploy dashboard.
Once on the Deploy dashboard you can update the URL params to "latest" & "previous" to compare any two test ids.
You can find the test id for any test by looking at the URL when on the Test dashboard or via our API. Here's the test_id highlighted in the URL...
Once you have a couple of test ids, go to the Deploy dashboard and add the latest/previous URL params to compare them like this...
From the Deploy dashboard you'll then be able to download a filmstrip comparison image or video and compare metrics to see what has changed and by how much.