I came across this dated article that seems to provide some insight into the differences. Unfortunately, it also seems like this information is held close to the vest by various manufacturers or perhaps only detailed at continuing education type conferences. Because the article is 10 years old, it may speak more toward a manufacturer's philosophy than how exactly the algorithms work today and now so please take it with a grain of salt.
I would also be interested in any other information folks have on the algorithms. At the end of the day the algorithm is key, but also the most difficult piece of information to uncover.
http://www.sleepreviewmag.com/2009/09/au...-pressure/