I am a software developper. My laptop is a ThinkPad W510. I spend 8 to 10 hours a day on my computer. I bought the Samsung BX2335 monitor yesterday. I am returning it: I can barely read while I am writing! This is my first experience with a LCD/LED...I am dispointed. In the past, I have always been extremly sensitive to frequency: working 10 minutes at 60hz on a CRT monitor gave me migraines.
So now, what do I do??
I am considering buying:
Samsung PX2370 23-Inch Widescreen LCD Monitor with LED Backlight
or should I buy a gaming monitor that has 120hz frequency to do software developement?
Samsung stuff is generally pretty good and Acer gets a mixed press.
I may be less sensitive to frequency than you but I have only once found a flatscreen which made me feel uncomfortable (and that was an AOC somebody had discarded) whereas I never felt happy with CRTs.
Most LCD operate at a native 60Hz -- but it may help you to select one which runs faster, though I doubt if your laptop will be up to it. As for size of display that is in your hands -- see the screen's OSD and Windows, Control Panel, Display Properties.
The complication in your case is that you are using a laptop -- where the video controller is presumably designed to drive the built in screen -- once you start adding much larger external screens problems undoubtedly occur. I have a laptop linked to a 19inch CRT and it looks pretty poor but, thankfully, I only use it for short periods in that configuration.
A 120Hz monitor will not matter if your Thinkpad does not have dual linked DVI output. Each DVI works at 60Hz.
Frequencies work differently on CRTs and LCDs. In CRT monitors the screen is refreshed from top to bottom; the higher the frequency the faster the refresh. LCD monitors do not work that way. Pixels in a LCD screen do not refresh unless it has to which is caused by changes to what is being displayed.
For example, if your are typing a document on a CRT monitor, the entire screen refreshes based on the refresh rate. On a LCD screen, the only thing that "refreshes" would be the area of the document you are typing. The white background would be replaced by the letters you are typing. Everything basically remains the same.
To simplify things a bit the only thing that flickers in a LCD monitor is the backlight whether it is LED or traditional CCFL (florescent).