Well, not to sound biased, but generally speaking anything out of Redmond is badly designed rubbish designed with the sole purpose to make $$ not to make customers happy, so I would tend to lean towards Snow Leopard
Seriously, if Microsoft were a car company, they would have been sued into oblivion with "lemon law" litigation. People are so used to the way their Windows computer works, or doesn't, they assume that's the way it is supposed to be.
I have been a Linux and Opensource user for more than 10 years and recently switched my primary system to an aging G4. Nothing Microsoft has ever come up with can even hold a candle to this system in terms of stability and useability IMHO, and I am running Tiger on an 8 year old DA.
I know this probably wasn't supposed to be a bashing thread but I get so steamed when Microsoft products are compared to "real" software like OSX, Linux or BSD.
I'll get off my soapbox now, sorry if I offended anyone.