As someone who processes a lot of bugs, I'd prefer to keeping using an interface and process I already know as opposed to one I'd have to learn (and possibly help define).

I see the distinction as one of scope, rather than one of 'newness'. Specific, resolvable enhancements (whether to existing features or for new ones) should be in Bugzilla, while more generic requests, or requests with much larger scope should be discussed on a 'brainstorm' site and turned into a series of specific requests to move to Bugzilla.