PAG's are very good in compressor applications, but I wouldn't use one unless the severity of the application demanded it. You get into a whole lot of side issues - they are not soluble/compatible with hydrocarbons, so if a sleepy oiler on the C-shift inadvertently tops up with a hydrocarbon (mineral or synthetic), the guys on the A-shift will have a bad day.
To convert to a PAG requires a scrupulous flushing procedure to prevent deposit formation. They are also not cheap, especially if you buy the private label rebrand.
The optimum compressor oil is going to be very application specific. Like the man above said, you need to provide more data for the best answer.