I went from a PC based system to a stand alone, mostly due to power consumption.
*Powering a P4 24 hours a day with multiple hard drives was a huge power drain, vs a stand alone unix based dvr. Since I was using the CCTV as a media server, I debated putting in an SSD for the recording part, but after crunching the numbers, the standalone paid for itself in power usage alone.
*PC based is vastly more configurable (1080p output, masking/delay options, playback flexibility, etc.) For example, on the PC I could highlight the motion captured frames and play those back, while on a constant recording. On the standalone, its either motion record or always on, at least on the consumer level device I bought. One nice feature with either system, is that if you are watching TV and the doorbell rings, you can switch inputs and see whose at the door.
*Bundled cameras usually aren't very good quality. Most will not be able to read a license plate at any significant distance. Face quality is tolerable. May be worthwhile to buy the DVR and cameras separately for better quality. As a deterrent though, any camera (even a fake one with a blinking light) can be quite effective.
* You could do a mixed setup with an 8 channel DVR (most standalone DVRs have PTZ controls), run 4-6 fixed cameras, 1-2 PTZs (to read close up stuff). Standalone cameras usually have good IR emitters already, though you can light up more areas with a separate IR illuminator (amazon sells these for about $40 bucks).
*I have 2 redundant systems, 1 that records the exterior of the house, I have another hidden system that records the interior of the house. This serves two purposes. Intruders will never suspect two systems. Once they break in, they may disable/smash an accessible cameras, dvrs, alarms, etc. No one expects a redundant DVR. See second purpose below.
*DVR location. Some people put them in lockboxes, bury them inside of drywall, etc. I think that is a fire risk. I'd rather go with 2 systems (exterior and interior). Even if they find the main DVR and smash it, I have a second system recording their identities. Most important, in a full scale perimeter breach, where your exteriors are disabled, and you have to shoot it out, having a redundant second system allows you to mount a considerable defense since you can monitor their progress at all times.
*Integration with alarm systems. Most stand alone systems integrate fairly easily with alarm systems, so you can have your alarm dial out if motions are triggered. The PC based ones, at least consumer level, are just PCI cards with video output. Both systems can send you text messages/emails, or allow you to view them with internet explorer remotely.
One great bonus of having a CCTV setup, the UPS and Fedex drivers also leave the packages in view of the cameras. I've never had an "attempted" delivery.