I've got one of each... Whilst I agree that 16:10 (or better yet, portrait monitor) is sometimes beneficial for many windows uses, since a lot of apps use a portrait layout, there isn't really a huge difference. For example.... if you want more vertical space on your 16:9 screen, just stick the taskbar on the side instead of the bottom, and get used to it being there. People saying they'd NEVER use one or the other are being a bit excessive... it's only about a 10% difference between them... not exactly a show-stopper.
But yes for viewing fullscreen media, I tend to watch 16:9 or above films/tv on the 16:9, and 4:3 stuff on the 16:10... it just makes sense.