Commonly people think that a processor with more Mhz and Ghz is more powerful and will do a better job, not necessarily. This short write up by CoolTechZone gives us some more insight into this and above all, it is readable, meaning that you don't have to be an engineer to be able to understand what the author writes. At the end it depends on what kind of applications one is running on the system or is intending to run.
Tejas Patel