[Paul]

between a "regular" reply?
well, yes, other then the lack of visible vB controls... not much.

but in a "regular" reply (if you get there by pressing a "quote" button) you also get the post you are replying to actually typed out in the reply box rather then (optionally) added later like in quick reply...

The only other difference that I can see is the text color when you are typing the post... (grey vs black)

oh, and you can only disable smilies, un-link URLs, edit posts, and change your notification regarding your subscription to the thread (the default is set in your user preferences) from the "regular" reply page... (assuming the edit page is the same as the reply page)

you can also edit the title of the post, but that feature isn't used by AN...