This is a bit of a hairy topic since there are those that prefer 16:9 and those that prefer 16:10. However, 16:9 is becoming more popular purely because companies can mass produce them and put the same panels into TVs as well as in monitors, hence the size being cheaper and thus more people buy it.
Companies are generally marketing 16:9 to be "better" because when viewing 16:9 content on a 16:10 screen, you'll naturally get letter boxing or black bars. However in my opinion, movies generally are not in 16:9 format anyway (usually a lot wider) so you'll get black bars regardless, just smaller ones on a 16:9 screen.
I would much rather have black bars which I can easily ignore if you're watching a film for example than not have the extra height you get. These days it's common to have 1920x1080 (16:9) vs 1920x1200 (16:10), that's a 120 pixel difference in height - whilst that may not sound much, in practice it's a lot. It's not like you spend more time watching movies or some other 16:9 content than general web browsing or playing games, especially not on a PC monitor.
However the 16:10 resolution has become a premium feature now so you're expected to cough up more cash if you want it. For me, I much prefer 16:10 and I don't even use my monitor for productivity (i.e. design work or programming), but I cannot afford it. This annoys me as 1 or 2 years back you could have paid the same amount now for a reasonable 24" monitor, but for it also be 16:!0.
Mayfair, check out
this video, it compares the 23" Dell U2311H (1920x1080 16:9) and the 22" Dell 2209WA (1680x1050 16:10), you can see the screen space you gain/lose. The video is stretched though, which is a little ironic considering it's somewhat comparing aspect ratios.
I've also noticed the premium they expect us to pay for the 16:10 aspect ratio.... 
