pm & r vs. gas -- pain management

From previous threads I have learned that a pain fellowship in gas or pm&r is a possibility for pm&r grads. What are the differences in gas vs. pm&r fellowship training? What is the scope(procedures, day to day work,etc.)of the practice of a pm&r pain specialist vs. a gas pain specialist? And finally, how are they similar or different viz a viz job opportunities, salaries. Thanks in advance.
Source: Student Doctor Network - Category: Universities & Medical Training Authors: Source Type: forums