Mac OS X's frameworks and popular Mac apps deftly distribute the compute workload across CPU cores, threading engines (in the case of Core i7), and GPU shaders. Users will find that Apple's combination of leading-edge technologies from Intel and AMD add up to a smooth, exquisitely responsive driving experience. As nice as it is under Snow Leopard, it's almost sinful under OS X Lion.
Thunderbolt iMac: Benchmark results If you're considering pressing a notebook into desktop service, iMac's superior performance should factor into your decision. Benchmarks comparing a 3.1GHz 27-inch Core i5 iMac to a 2.2GHz Core i7 17-inch MacBook Pro show iMac to be the clear performance champ, and the thread-intensive SPECjbb2005 benchmark doesn't even highlight the benefits of iMac's desktop-speed hard drive. Although it's possible to configure high-end portables like MacBook Pro with a 7,200-rpm hard drive and an upgraded CPU, you'll spend a lot to construct a notebook that's in iMac's league.
I don't have a current Mac Pro for testing, but benchmarks run against an older eight-core Nehalem Mac Pro reveal iMac's generational advantage. The iMac scales remarkably well to SPECjbb2005's multithreaded workloads, even when pushed to run eight threads without the benefit of Hyper-Threading. The iMac has the headroom to handle a demanding mix of foreground and background tasks without bogging down the user interface. (See the table of SPECjbb2005 results.)
Notes: Thunderbolt iMac configured with 3.1GHz quad-core Core i5 CPU, 6MB L3 cache, 4GB of 1,333MHz DDR3 RAM; Thunderbolt MacBook Pro configured with 2.2GHz quad-core Core i7 CPU, 6MB L3 cache, 4GB of 1,333MHz DDR3 RAM; Core 2 Duo MacBook Pro configured with 2.8GHz dual-core Core 2 Duo CPU, 6MB L3 cache, 4GB of 1,067MHz DDR3 RAM; Nehalem Mac Pro configured with two 2.93GHz quad-core Intel Xeon CPUs, 8MB L3 cache, 12GB of 1,066MHz DDR3 RAM.