I've used both NVRs and
Blue Iris on a tower. There are pros and cons to each type. Based on my comparison here are my notes. Personally I'll stay with the NVR now as replacing the computers is more costly and brings with it unplanned/unscheduled security updates.
Computer as NVR:
++ recognizes virtually any camera type
-- may tax your CPU heavily since the CPU is doing the processing (more camera the harder the CPU works)
-- computers suck typically a lot more power
-- Microsoft updates shut down computer at inconvenient times
-- computer on network is easier to hack
++ can stream video over your VPN without needing to use an app for access
-- computer operating system requires a drive that will fail over time
++ can have multiple drives for video recordings
-- a cheap computer will not have a CPU able to support 16 cameras all streaming video to be recorded 24-7
-- computers are not designed (unless server) to be ran 24-7 (my last one made it 2.5 years until it failed running 24-7 as a NVR)
Dedicated NVR:
-- you need to carefully look at specs to see what cameras work with your brand NVR (I have GW NVR that supports ONVIF but not all cameras, most good cameras do though, support ONVIF)
-- you need to carefully look at the specs for recording mp bandwidth rate
++ uses minimal power running 24-7 compared to a computer pulling 200+ watts
++ No unexpected Microsoft updates shutting down system
++ dedicated NVR software not easier hacked
- -you need the NVR's app to access remotely
++ NVR operating system is not on a drive thus a drive failure only deletes old recordings
-- limited to number of hard drives for video storage (I have 2-10TB WD purple hard drives recording 16 camers recording 24-7 giving me only 42days of storage: 1-4k 20fps, 15-4mp 20fps)
-- a good NVR can be costly. Mine on sale cost over $300 (POE but I used POE switches instead of buying a 16-port POE NVR)
++ NVRs are designed to run 24-7 without failure (My current one is running 24-7 and records 16 channels 24-7 for over 4years now without a hiccup)