I'd have to agree with kipster. The price tag of NUC's (used and new) are exuberant as compared to PC's. I had this decision thought process when I wanted to move away from my i7-4770 CPU based Dell optiplex Mid-Sized tower. Not sure why NUC's are so spendy since they take up less material to manufacture. But the USFF I selected was $200-$400 cheaper than equivalent hardware spec'd NUC. I also feared the CPU heat buildup since IP camera and video compression really hogs up the CPU utilization in a NUC. I believe, you will find additional posts here about the pro's / con's. Most, seem to lead towards the 'not so great of idea'.
When I first jumped into the camera arena last year, I too was about to pull trigger on a NVR. Luckily, I opted for
Blue Iris on a PC. More options, control, security, etc. Of course that means more learning, more headaches, more configurations, etc. Ying/Yang.