First off, there is no such thing as LED vs IPS. IPS screen can be either LED or LCD. In sum, many IPS monitors use LED and LCD pixels. The actual comparison is TN vs. IPS, since TN monitors can also use LED and LCD pixels. . . . But more important is the comparison between these two monitors, since that is your question.
You just have to look at the specs. I've bolded what's most important.
Here are the specs for the 23-in monitor (IPS monitor with backlit LEDs):
Screen Size 58.4 cm (23")
Screen Mode WXGA
Response Time 5 ms
Aspect Ratio 16:9
Backlight Technology LED
Video
Maximum Resolution 1920 x 1080
Contrast Ratio 100,000,000:1
Interfaces/Ports
DVI Yes
HDMI Yes
Warranty Standard Warranty
Viewing angle: 178°
Standard Refresh Rate: 60Hz
Here are the specs for the 24-in monitor (TN monitor with backlit LEDs):
24” Screen
Panel: Twisted Nematic Film (TN Film)
Backlight: LED
Resolution: 1920 x 1080
Aspect ratio: 16:9
Response Time: 2ms
Brightness: 250 cd/m²
Contrast ratio: 100000000:1
Viewing angle: 170°/ 160°
Display Colours: 16.7M
Standard Refresh Rate: 60Hz
So you are looking at two 1080p monitors with backlit LEDs, both of which have a similar viewing angle, and both using 60Hz refresh rate. The main difference is the panels. The 23-in uses TN panels, and the 23-in uses IPS panels. That difference accounts for the fact that the 23-in monitor has a response time that is 2.5 times slower than the 24-in monitor (5ms vs 2ms). The response time measures how long it takes a user input to react on the screen. So, if you click the Windows Start Button at the
exact same time on both monitors, the Start Menu would pop up slightly sooner in response to your click on the 24-in monitor than on the 23-in monitor. The actual difference between the monitors of only 3ms would be slight, though, since 3ms is a very short time (i.e. three one-thousandths of a second).
As for color, the only way to tell which produces better color would be to color calibrate both monitors, set them up right next to each other, and then display the same thing, running them both as a mirrored display setup from the same source. Unfortunately, you can't do that unless you buy them both. They both "display 16.7 million colors," but that only means they are compatible with the SRGB color standard. The short explanation of that is that they both work as standard monitors, but not as graphics professional monitors. One suggestion if you really want to compare how color-accurate they are is to actually order them both from a vendor that allows free returns (e.g. Amazon). Then you can create the setup I described above for a true side-by-side comparison. In order to color calibrate, you'll need a calibrator tool. Here are some (the best brand is X-Rite): http://www.amazon.com/s/ref=nb_sb_noss_1?url=search-alias%3Delectronics&field-keywords=x-rite%20display&sprefix=x-rite+di%2Celectronics&rh=i%3Aelectronics%2Ck%3Ax-rite%20display.
Good luck!
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