I am running some image processing c++ code that processes and generates a 320x200 pixel image. The program uses the openframeworks API for display. If I run and compile this code on my Macbook Air (i7-2677M, 4GB RAM) the rendering runs about twice as fast as on my Desktop i7-2600 (16GB RAM) (a PC, not a Mac machine).
I have compiled and run the code on the Mac using Xcode 4, and on the Mac also in Visual Studio 2010 running on Parallels VM software, 64-bit Windows 7 - both compilations give roughly the same speed.
On the desktop side I have compiled using Visual Studio 2010 on 64-bit Windows 7 and also using CodeBlocks running on Ubuntu Linux. Both run noticeably slower than the Macbook Air.
I have run two benchmarks using PassMark and NovaBench on my desktop and both times the rating came out as a sensible number, giving roughly twice the performance over the same benchmark run for the Macbook Air and matching comparatively spec'd machines.