o believe a wider gamut would be better for previewing video on screen, as it is closer to the gamut of HD TV's.

a narrower gamut as sRGB is better for photo editing i believe, as the final print would be closer to what you see on the screen (prints have also a shorter gamut)

Malows, this is complete understanding of the problem.
Wide gamut monitors are mainly used in graphics, because they can display wider colorspace than the sRGB monitors. The wide gamut monitors usually display 99% of Adobe rgb colorspace. The biggest advantage of the wide gamut monitors it that they can display CMYK colors, or just emulate any printer. So after applying the printer's color profile, you can see, how the image will be finally printed on a specific machine.
Wide gamut monitors may be also trimmed to sRGB color space and emulate colors only from this colorspace.
The disadvantage of wide gamut is that you need to constantly check and switch your color profiles for different output devices. So if you don't want/ don't know how to do it, buy sRGB monitor. Because, using a wide gamut color spaces like Adobe RGB, needs a software that accepts easily color profiles. Without it you will not be able to use the advantage of wide gamut.
If you are planning to use the new monitor for preview purposes, you have to remember that Vegas pro works natively in sRGB. So sRGB monitor is enough for this software. Of course wide gamut one will also work properly, however you need to calibrate it first to trim the colorspace to sRGB.
If you want to emulate some video colorspaces like for example rec. 709, you will have to buy widegamut monitor, decent calibrator and video card. In this configuration you will calibrate the monitor as TV and send the signal in rec. 709 colorspace form the video card. Also you have to check if you monitor accepts interlaced signal if you want to edit one.

Thanks for the information.
Is there any benefit to having a monitor capable of the DCP-P3 Digital Cinema Color Standard outside of Vegas (Vegas being limited to sRGB)?