PDF/A1-b or PDF/A-2b?

Question: Is it recommended to use PDF/A1-b or PDF/A-2b?

Answer: PDF/A-1 is based on PDF version 1.4.  PDF/A-2 is based on the latest PDF standard which supports more functionality and better compression than the older format (compressed object streams and compressed cross reference streams for example). With this in mind, we recommend PDF/A-2b.