My cute answer is "both". However, there's a major problem with using MassEditRegex: the regex doesn't have access to the page's metadata, only the page text. The page title is the important metadata in this context. I suppose it would be possible to do it in two edits with MERx: the first to add something like "" to the page, and the second to extract the title information and replace it with a proper {{DEFAULTSORT}}. If all you have is a hammer, eventually you'll knock that bolt loose.
But really, bots are the right choice. I've never actually used AWB, but I assume it can do it? I'm running a major link update now -- I think I was two whole years out of date on that. In passing, if it notices a page without a sortkey, it will go ahead and add one. This is one of those jobs that will edit in the thousands of pages, so I should solve some of the problem today.
-- ∇×V
But really, bots are the right choice. I've never actually used AWB, but I assume it can do it? I'm running a major link update now -- I think I was two whole years out of date on that. In passing, if it notices a page without a sortkey, it will go ahead and add one. This is one of those jobs that will edit in the thousands of pages, so I should solve some of the problem today.
-- ∇×V