So I just did all my updates and got new drivers and quicktime installed on my Win 7 partition, and now I can run the same 3 layers of 720/1080 DXV clips at a stable 60 FPS vs the 20-30 I was getting in OSX...
Is this a driver issue? I find the same is generally true of games...
We (unfortunately) also see this performance difference between OS X and Windows. Hard to say what is causing this but it's indeed true for most games and cross-platform apps. OS X is great but it's definitely not the fastest.
I think this is mostly related to the OS/driver handling of 3D apps.
Apps like photoshop that have limited GPU rendering seem to run perfectly fine in OSX.
Hopefully Apple or the vendors can sort this out.
In the mean time, there's boot camp