There are many aspects to computers performance. Computers are like cars - complex systems with many components. Having more of one thing, without the balance of the other sub-systems, doesn't mean the whole will be much faster.
Computers are the same.
They systems performance is actually the sum of its flaws. PowerPC's usually outclass their Pentium Counterparts. Intel tries to dazzle and confuse users with flying computer graphics and pretending that Pentiums have created the MultiMedia revolution - but fail to mention that those dazzling Pentium commercials were made on Macintoshes, and Macs had multimedia for many years before PC's got the same. Those will be your real world results. To understand performance one must understand what each of these sub-areas of performance are and how they work.