- I can deploy them using GPOs that map the TCP port with the printer's IP address (how I'm doing it now
- I could deploy them using Print and Document Services and AD
- I could deploy them using the "Deploy Printers" in GPO
All three use group policy to actually do their thing. #1 uses a User policy, in the Preferences section, to set a direct-IP printer. #3 uses a Computer policy to push a Network Printer based on a print-server somewhere. Not quite sure what #2 does that the other two don't.
The first option means that you have no central control over the printing environment. People just print to their local printer. You don't even get any kind of driver-level control, end-user workstations will just use whatever driver is at hand. Over time they or their techs may install different ones from computer to computer.
The third option means you have a central print-server (or maybe a printer on a workstation that you're pushing out to people, whichever) and you can control a lot more about it. For instance, you can control who can print to that printer; important if the printer is a Large Format printer (plotter) that you only want a few people to be able to print to it. You also get centralized driver control, which makes your print-driver environment for that printer homogenous.
The first option has no central point of failure other than the GPO process itself. The second option relies on a print-server being present (which can be any Windows computer, workstation or server) somewhere in the chain. The first means that anyone can print to the printer if they take the time, you're just automating the process. The second allows you to prevent people from printing to certain printers (assuming you've locked down the printer itself to only allow printing from it's Windows station).