That interval is the refresh rate. A better monitor will support higher refresh rates at a given resolution. Refresh rates drop with higher resolution because the tubes take more time to sweep across the greater number of pixels. Good monitors will stay at a reasonable refresh rate of 75Hz or higher, even at the highest resolutions. TFT displays offer less distortion and excellent viewing for common computer applications.
Power consumption is a third of conventional CRTs.
TFT prices have dipped quite a bit since they were introduced. A TFT screen uses a panel of many pixels, with each pixel able to emit any color. So for light to reach the screen, it has to first pass through several filters before images can be displayed. Less radiation is emitted, and thus there's less strain on your eyes. And if desktop space is an issue, a TFT screen is what you should get.