I'm currently in a very similar situation choosing between offers for a Masters at Stanford or a PhD at UCLA in Electrical Engineering.
For EE as well, Stanford is definitely at the top of the rankings... but of course, there's the question of funding, or lack thereof that's being offered with the Masters program. Whereas UCLA is offering me a full fellowship. I agree it's a pretty tough choice.
I'll be making my decision soon as well and I'll likely be following this thread for more opinions. Thanks to everyone that's posted already - there's been some really insightful advice. And good luck feelgoodhit with your decision