The honest answer is that most new installations should be IP, and most partial upgrades should not rip out working analogue infrastructure on principle.
Where IP wins
Resolution beyond 2MP, analytics at the edge, single-cable power and data, and central management across sites. If any of these matter, IP is the right call.
Where analogue still earns its place
Existing coaxial runs in a building with no cable route for new Cat6, low camera counts and tight budgets. HD-over-coax technologies now deliver 4K on existing cable.
How we decide
We start with the retention policy and the incident types you actually need to resolve, size storage and bandwidth from there, then pick technology, not the other way round.