Let me preface this by saying that I have not yet attended PASS, will be this fall, but I have attended other conferences that have a similar format.

For the PASS Networking opportunities it really is both for me with probably the opportunity to have some of the top SQL Server people as resources when I do have an issue I don't understand as the first reason. Sure you can use Twitter/LinkedIn/Forums, but a an email to a specific person with expertise in the area would probably be the fastest way to get an answer. Of course, you have to be just a willing to help out when you are perceived to be the expert.

Based on what you have shared, if I had to choose one, I'd take the class. For the original reasons I shared.