Two technologies, two signal paths
An analog system sends its picture over coax cable (usually RG59) to a DVR (Digital Video Recorder), in the AHD, TVI or CVI standards — different names for a similar idea, with most of the image processing staying inside the camera. An IP system sends its picture over a network cable to an NVR (Network Video Recorder) or straight into a VMS (Video Management Software), with the camera already outputting a digitally encoded signal.
The difference isn't only the cable. IP cameras generally run on ONVIF, an open standard that lets cameras and recorders from different manufacturers work together, while analog systems mostly don't need to ask that question because the signal is simpler.
What the existing cable can still do
An existing RG59 coax run isn't automatically scrap. An AHD/TVI system over it reaches 4 MP without opening a single wall — for a site that already has cabling in place from an older installation, that's the difference between replacing cameras and replacing the entire wiring run.
The limit is real: above roughly 4 MP, or once you need a PTZ (pan-tilt-zoom) camera with advanced features, coax starts imposing a ceiling that IP doesn't have.
Where IP wins
In new installations, where cable still has to be run, PoE+ (Power over Ethernet, the higher-power variant) carries data and power over a single line — one cable instead of two, and no separate power supply needed next to every camera. Resolution above 4 MP, on-camera analytics, and pulling multiple sites into one VMS login also sit more naturally on IP.
Interoperability via ONVIF also means the system is easier to extend later with another manufacturer's gear, without swapping the whole recorder.
The tradeoff: cost against room to grow
Keeping the existing coax run saves the cost of opening walls and pulling new cable — usually the biggest line item nobody plans for in advance. The price of that saving is a ceiling around 4 MP and a system that grows less easily past it.
A new IP system costs more upfront, since cable still has to go in, but it sets no ceiling on resolution or on how many sites can sit under one login.
Recommendation
If a site already has coax cabling in good condition and 4 MP is enough for the job at every position (see the pixels-per-metre rule), AHD/TVI is a legitimate choice that protects the budget. If it's new construction, resolution above 4 MP, or several sites on one login, IP is the answer you won't need to replace in a couple of years.
We check the condition of any existing cable during the site visit and say plainly whether it's worth keeping.