yeah, benchmarks are the onyl real way to compare processors. Using conversions to try to relate mhz numbers is very innaccurate. Each different type of CPU architecture favors different types of programs, some are very dependant on pure mhz, others on instructions latentcy, or cache size, or cache speed, or memmory bandwidth, etc...
So, basically benchmakrs are the best comparison. The onyl thing to keep in mind with benchmarks is if they apply to what you are doing. So if you are only using a computer to browse the internet and use word then who cares how many FPS it gets in BF2?. Also, keep in maind that what processor wins isnt always as important as it seem, all the time i see people claiming that AMD pwns Intel in gaming, but that is only by a few percent, and onyl at low quality settings with a great graphics card. In most games your CPU will only have a small change in your FPS so long as it isn't completely outdated.