Does it really matter how well or badly OS X or Linux does in benchmarks against each other? I think it depends on what the specific install of whatever it happens to be is being used for.
For example, if the box is being used to encode video, then by all means use whatever is providing the best return for resources being given. I mean, Hollywood does this all the time with Linux boxes. So I see little reason to change this now.
There are other areas as well in which having the right OS based on its performance is key. Encrypting data, data transfers from one location to another, and so on. At the end of the day, I think that for most people the OS being selected continues to be less about how fast it does select tasks, rather being an issue of how it does for the end user with regard to overall usability. I say this as I use both 32bit and 64bit Linux. Because of my casual desktop usage, I simply do not see the difference in my tasks. Yet others using their systems in such a way as 64bit would be fully used, would see the difference. Different strokes for different folks.