I've ran through the performance numbers announced by IBM and what I found at spec.org (specint_rate & specfp_rate) of the other CPU's and roughly the following picture (give/take 20%):
- Power6/Power7: about 30 spec_int/fp_rate/core
- Intel Core i7: about 30 spec_int/fp_rate/core
- Sparc: about 10 spec_int/fp_rate/core
- Itanium 2: about 12 spec_int/fp_rate/core
So it looks to me that performance-wise Power and x86_64 are similar. Both seem almost three times as fast as Itanium/Sparc. However. in the commercial world scalability matters and I there are not many big (>4 socket) x86 systems around. Big Power, Sparc and Itanium servers scale to hundreds of cores and are built like mainframes with excellent RAS features. I see high-end kit from both sides, x86 and Power and the margins in the x86 world are not good enough to pay for the engineering it takes to get to the same levels.
If you compare Power and x86_linux with cars:
- You are read to spend some money to drive a nice car with excellent performance and stop at the dealer for inspections regularly then you well of with a Range Rover (=AIX Power server).
- You are going to cross Africa, will be on your own (and have the truck full f spare parts) and are ready to get your hands dirty then you want a Land Rover (=Linux x86).
This picture is far from complete, but shows what the choice is quite well.