What is the reason for choosing a different print processor?
Way back at the beginning of Windows, Windows printing was not considered reliable. The standard to which it was being compared was NetWare (this was the 1990's after all), which at the time had a good reputation for reliability. Because of this printer manufacturers created their own Print Processors under the impression that:
- They could do it better than Microsoft
- By owning more of the print-stack they were better able to control the print environment and produce more repeatable results
- Certain windows-isms could come into play for remote printers (such as those hosted on a central print-server) and local printers, where the same job can render differently based on local/remote status
- They could provide advanced print features, such as toner-out notifications, internal hardware failure notices, and the like.
HP was prominent in this, and in fact still ships a print-processor with its drivers. Though in recent years their 'enterprise' product line has seen this less often, where their consumer product line tends to rely on it more. This has the side-effect (likely intentional) that their consumer product is a poor team player on centralized print-servers.
The Windows print-processor has gotten a lot better over the years. Even so, there are still some instances where a custom processor is needed.
At my old job at a large University, where we had something like 1700 computer-lab seats and printed about 2 million pages an academic quarter, we needed a custom processor for our print-auditing solution. As I understand it, it just acted as a shim between the spooler and the actual RAW provider that allowed for advanced features like tracking quotas and handling charge-back.
The above are for third party print providers that commonly come along with the driver install. Windows has its own providers, and I've rarely seen things set to anything other than "RAW".