Well, (and we can rail back and forth on this for days... :-)), the GFv3 Feature thread is a specific example.
On the forum, the formatting is essentially destroyed by a particular post that makes it extremely wide. So there's no (very little) line wrapping.
This in turn appears to have ruined the "nesting" display of the topic, so it's difficult to see who is replying to who.
And, finally, because of the nesting, when new messages are added, you can't easily find them. Case in point, last time I saw the v3 thread there were something like 62 messages. Now there's 67, but only one of those is at the bottom. No idea where the rest are, buried deep inside somewhere (I don't normally subscribe to threads to be notified by email -- I just check back over time).
Using the mailing list, in theory all of the old messages would be marked "read" so I'd see the new ones more easily.
Also, there's a struggle between the forum posters and email posters.
You can readily see the email posters "top posting" all the time. That is, they see a post, hit Reply, (which quotes the entire message), then they rattle on a bit at the top and send the whole kit.
This works for them because they see a single message at a time, and they only see the top of the message. They never bother scrolling down to the bottom. All of the cruft of the reply (as well as the earlier replies -- each message is the entire thread! Look, you can count the >> to see how old it is!) is hidden outside of the message window.
But we poor souls on the forums, we're stuck. We get to scroll and scroll and scroll past all of that cruft.
Forum posters have to take action to quote the post (most don't -- I didn't here for example, as the context is readily apparent through the display in the forum software), so the messages aren't as nasty and junk filled.
So...from the "can't beat 'em, join 'em", I may simply subscribe to the mailing list and be done with it.
It can certainly be more difficult to track the fibers of a long thread in email as they diverge a bit.
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