Everyone in a while we're looking for new publications about Betterbird. We found this video, which stated the following (quote, 4m22s): It's what Thunderbird could have been if development moved faster and user feedback was (sic) prioritised.
And no, we didn't commission the video and we also don't know the guy and never had contact with him. Also, not all the good claims about Betterbird are true, apart from punctual changes, the performance should be the same as Thunderbird, however, some people start Betterbird on a new profile which may be faster.