Earlier quoted context omitted.
aerc doesn't download all of your message headers upfront - mutt does. All that time you spend waiting for mutt to open your inbox is downloading all of the data that aerc is downloading as you scroll. Also, you can scroll faster with ^d/^u, half a page at a time, or pgup/pgdown, for a full page at a time. Yes, aerc is not yet as featureful or mature as mutt, but it definitely does not have inferior performance.
I use POP3, and only wait for mutt when changing to a folder (4s/100k mails). Then everything is basically instantaneous. But yeah, I don't know about mutt IMAP performance, as I never used it. I've only configured a local IMAP server over my maildir to be able to try aerc. I have no clue why aerc is taking 100-200ms to load a single message (as you see in the video) from the localhost. Maybe naggle (is it even used…
aerc will also support maildir before 1.0, which doesn't have the same issue, and will be at least as fast as mutt.
>Also, I'm not sure how you'd make threads work while loading message list only partially. So full load of the message list is needed anyway (at least once and cache it locally). It's not some failing. I want thread that started 5 months ago to pop forward if new message is posted to it.
IMAP has a thread extension I intend to put to good use for this purpose.