Peter, 

The 5-20 and 6-20 license are the same thing.  The license converts to the job you hold. If you are working for a specific company, you hold a 6-20 license and if you work independently, you hold a 5-20 license but it's the same license on paper. 

Job prospects? - most companies want their adjusters to start on a first response team. however many companies train on-the-job for catastrophes.  

Jan