Why do imacs run slowly?

Wired News asks Why Do New iMacs Surf So Slowly? which reports that the new iMac 2's are not barnburners in the surfing department.  The article blames OS X, but whether it's hardware or software, I've known for years that iMacs are slow.  I did a little test around our house, and the Win98/PI/133/64MB running IE 5.5 in the basement surfs at about the same speed as the 400mhz/128MB G3 iMac OS 9.1 iMac in the dining room.  (And the P133 was faster at a few sites.)

My favorite quote, especially since we just bought an eMachines box to replace an iMac:

I spent $1,800 on a computer that's slower than the $400 eMachine it replaced," one iMac user wrote in an e-mail.

A few conclusions from my non-scientific tests here at home:

• Mac IE 5 and Netscape 6.2 were about the same speed for more tasks, with a few exceptions.  (Loading my tax return off the Turbotax web site was twice as fast in NS.)
• The P133 was as fast or faster than the Mac on almost all tests.
• My P3/500/256MB running Windows 2000 and IE 6.0 was about twice as fast at rendering pages as the iMac or the P133.