I also went with a 4:3 instead of widescreen, and I think that I am glad that I did. If I need more screen space width-wise, then I can just add another monitor.
I never saw a game playable in 1440 x 900!!! Serioulsy. It's always 1600 x 900 or the 16:10 format 1650 x 1080. I would go for another widescreen monitor.
If you watch alot of movies, then widescreen would probably be better. However if you play lots of games, 4:3 is the best IMO, also because alot of games only support 4:3.