Yes, because people love to read long pages of text and never just click the first button at the bottom of the dialog. More importantly, plenty of Firefox users don't know they're using Firefox, or don't care, and won't know how to react to such security notices.

The first notice is much simpler: users will recognise that they are 'upgrading' to a new version, almost all will allow it, and people who don't like the awesomebar or something have the option to deny. The second notice is just confusing to novice and casual users.