For editing photos, you need a monitor that gives you an accurate representation of the colors of your photo. So, it is worth spending more on a monitor that offers a wider color gamut and which can be more accurately calibrated.
For those with the budget to spend, a monitor that includes a built-in calibrator, such as the Eizo ColorEdge CG245W will be a good pick. This includes a calibrator that flips down from the top of the screen, which allows you to regularly check and recalibrate the monitor to adapt for any color shift caused by the monitor aging.
A wide gamut monitor is also a good pick, as this means that the monitor can display a wider range of colors than a normal monitor. Most monitors can display the sRGB gamut, but some monitors can also display the larger Adobe RGB gamut, which means that they can show a wider range of colors. Either way, the monitor should be set to show and calibrated to the same color gamut that the images were originally taken in to preserve the range of colors that were captured.
If you buy a monitor that does not include a calibrator, you should invest in one. We use the $250 iDisplay Pro to calibrate all of the displays that we test, but alternatives are available, such as the $200 DataColor Spyder4.