Timely thread. I am on the verge of installing Night Owl 8-camera system, which I bought at Costco 18 month ago. Just got around to doing it. My system is DVR with cameras connected by siamese video and power cables. At the time when I bought it, I didn't know about NVR v. DVR difference. I wish I had NVR system, because the wiring is much simpler. I can easily install Ethernet connectors and wouldn't need to drill big holes in my brick walls to pull through cables that connect to DVR.
Is there any advantage of my DVR system over NVR?
There's no advantage to a DVR over an NVR, in fact the opposite. You still can use cat cable instead of the siamese cable, you just need a pair of baluns for each camera https://amzn.to/2RHwD4L