It doesn't feel the same. Unless one is nearsighted and/or crosseyed, it's easier to focus and converge on a more distant object. It also provides for a lot more desk space in front of the monitor.
I have 2 24" monitors at work in portrait mode and bezels are my bane. I would much prefer a 30" (or hell, 50") with no bezel.
With my main MBP display as a good 2nd screen (great for telecons where you share one screen - you can keep your side-channel chats and email private on the other), one large main screen is perfect.
