Just because both clock speeds are 3.4GHz, it doesn't mean that they are the same. For example, the AMD Phenom may require more clock cycles to do the same amount of work as the Intel i5 one. Hence why the Phenom one is slower. So unless you're comparing the same exact product, there's no reason to look at just the clock speed.
The i5 has a newer arch, is overall faster in both single-threaded and multi-threaded applications, comes with a HD 4000 GPU whereas the Phenom doesn't have any, has higher OC speeds, runs cooler, and uses less power.