Think if you get a lot of responses to this, you will get opinions on both sides. On this one, I like bigger is better up to a point. Between work and home I sit in front of a computer screen 8-12+ hours a day. I work in excel 6-10 hours a day with a 21" and if I could get them to buy a 30-32" screen, I would take it in a heart beat. The 32" I had at home was great, for most everything, particularly for watching HDTV and movies. Was not so good for gaming while sitting only 2-3' from the screen. With games that have info at the sides, top, bottom that you need to be aware of, found myself having to push my chair back to about 5-6' from the screen to avoid having to spend time moving my eyes and head to get this info. This was time spent that could cost you in some shooters and racing games - the difference between winning/losing. Have found the 24"-26" which I now have is just about right for sitting at 3' away. Am above the age where I now need glasses for reading. Have found that with the larger screen sizes, I can once again sit in front of my computer without glasses most of the time with only minimal to no adjustment of font sizes.
You really should go to the nearest Apple store and sit in front of each one with the primary apps you will be using. But, I don't believe I've ever heard any comments related to wishing they had gotten a smaller screen.