Even if I am not strong on that, I'd vote for enable by default. I admin that some of them are specific (like ciscodump or androiddump), but I consider others like sshdump and randpktdump pretty general. Having them hidden by default would limit their use. New users will never notice this new interfaces unless they careful read the release notes (and the average users don't). I guess that many people do remote sniffing on ssh connected machine and they will have great advantage by sshdump. We make software that should reach the users, don't we? What if it's hidden?
At the same time I must admin the list of extcap can became annoying long. For that reason some time ago I filed a enhancement on bugzilla to change the list into a dropdown menu.
From my perspective, this kind of enhancement would make the discussion and the preference itself obsolete. The extcaps would be enabled and shipped by default, but the look of the GUI wouldn't be cluttered.
Dario.