Think of it in reverse: When Intel was still producing the 32-bit PII, AMD was making the 16-bit K6. But the performance of the two chips was simular because Intels "300 MHZ PII" was running at 300 MHZ but AMDs "300 MHZ K6" was actually running much faster: more like 550 MHZ. The net effect was that it ran like a "300 MHZ" PII.
As for day-to-day applications most of the reasons you notice your wife's new computer running so fast is not the chip itself but the peripherals like the hard drive. You probably have a 3400 RPM drive and you wife's system probably has a 7200 RPM drive with UDMA 100. She probably has DDR memory too, as opposed to your memory which is probably running at 66 MHZ. Not to mention a superior video card.
Where the processor really comes into play is in rendering graphics or sorting large database tables...When opening Word or something like that, it's everything else in the computer that comes into play.
For a particular task, a computer does work at the speed of the slowest component involved in that work task!
Fast computers and slow computers all wait at the same speed!
The world of the Personal Computers has really come a long way. We are now rehashing many of the (nearly) same arguments that took place relative to mainframes and supercomputers some years ago!