Leo says the only reason to upgrade would be the SIV's gorgeous screen. However because of that, he'd probably lose some battery life going to the new phone. All things being equal, he doesn't really see a compelling reason to buy the SIV right now. The faster processor doesn't have that much of an impact either.
What about the Galaxy Note II? Leo likes the Note II a lot, but it may be a better idea to wait for the Note III. It'll have 1080p resolution, which will be worth it.