Well there's no denying iOS is the king of responsiveness in the mobile sector, but to be honest, I can't really say the same thing on OS X vs Windows 7. I use both on a daily basis and Win7 is definitely the most rock solid OS Microsoft ever put out. For example, when an application crashes Windows just kills it and everything is fine. On OS X when something crashes, you can usually Force Close, but sometimes the process just can't be killed. Also it feels OS X memory management almost requires an SSD nowadays.
There are other things, which makes me like OS X more, but being faster or more stable is not one of them.