IMO it depends on how organized you are and how often you need to access archived video.

LTO-9 is cheaper per TB (haven’t run the numbers, but on the order of 100s of TB it’s almost definitely true) but relies on someone physically finding the right tape and putting it into the system (unless you shell out for a very expensive automated system). Not good for fast access, but cheaper for expanding.

If you need fast, automated access I’d recommend the NAS option, but keep in mind that it would be in one physical location. A fire or flood and you’re fucked.

Plus, since the cost per TB of tape is so much cheaper than HDD, expanding your archive is probably much cheaper with tape (keeping in mind the organization/automation aspect)