Check out The CPU Scorecard - Top CPU Benchmarks & Comparison Scores and compare the performance of a PowerMac G4 clocked at 500MHz with the Intel and AMD processors. But don't ever forget that benchmarks are open to abuse.

In their Apple - Products - Power Mac G4 overview Apple, of course, are also selective in their choice of benchmark comparisons:

So how does the G4 with its Velocity Engine stack up against Intel? brand-new Pentium processor?

To find out, we went right to the source: We used a set of Intel's own performance tests published on their web site.

Using six of Intel's tests, the 500MHz G4 (with its 128-bit Velocity Engine) is over twice as fast as the 800MHz Pentium III.