- ... What else?
How about the ability to post/read/respond to messages even when you're not at your own computer? Many people on Yahoo Groups, for instance, don't even have a computer at home and access their groups from works or library computers. To my mind, this is probably the most important advantage a forum has over an email list.
Are Yahoo Groups allowing to access regular newsgroups? Supposing it is, making Wine's mailing a newsgroup would make it accessible through that service and others (ex Google Groups). I haven't used that feature, but I know Google Groups allows to rate posts with 1-5 stars.
I'm not an heavy newsgroup user, so I'll leave it to you to find disadvantages of using that approach.