Well, I always like new and shiny things, so I'll have to vote for the new MB/P's.
One thing to add, now that the screen border is gone, and the screen is better...can you see the black letterboxed areas when you watch a widescreen movie?
I like the thinness and the unibody of the new MBPs, but I'm gonna have to go with the old one. The biggest thing is, I never liked the design of the black display bezel. I personally find it visually distracting and difficult to use. I've been using my iMac now for 3 months and I'm not yet used to the feel of it. Also, the glossy screen is something that I detest. It looks pretty while the computer is off, but once it's on, it's full of glare and it's downright ugly. So, by a narrow margin, I'm going for the old MBP.
Yeah, seeing one in person...Or better yet, next to an old MBP is all you need to appreciate the design. Plus, the build quality! This new one is solid. No creaky keys when you type.