Are you planning to have the display showing the camera feeds 24/7? If so, I would say a monitor... for one it would be cheaper than a TV which has a tuner built in.
Personally, I don't plan to sit and stare at my CCTV system when I am home, so I am tying it into my TVs as an additional input. If I want to pull up the cameras, I can just change the input of the TV.
Additionally, I have LG TVs which are able to be controlled via RS-232 (ASCII commands)... which I can tie into my Elk system and have the TV input change automatically when the doorbell is pressed.