From what I have read I understand that the 200's are class AB/G. They are AB up to 80 watts and then G beyond that range. I have heard that this is called "rail switching" and understand the basic concept but wondered if anyone can give me a good explanation of benefits, drawbacks, etc.

Here is the thread you need:

http://ubb.outlawaudio.com/ubb/Forum18/HTML/000003.html

Contained within is an explaination by Outlaw about what all the switching is about.