This time, it was Popular Mechanics recently ran two comparison tests in its May 2008 edition. The desktop competition featured the iMac vs. Gateway One, and the notebook version featured the MacBook vs. Asus M51SR. You can read the full article HERE, but a summary is listed below, in Popular Mechanics’ own words:
In both the laptop and desktop showdowns, Apple’s computers were the winners. Oddly, the big difference didn’t come in our user ratings, where we expected the famously friendly Mac interface to shine. Our respondents liked the look and feel of both operating systems but had a slight preference toward OS X. In our speed trials, however, Leopard OS trounced Vista in all-important tasks such as boot-up, shutdown and program-launch times. We even tested Vista on the Macs using Apple’s platform-switching Boot Camp software–and found that both Apple computers ran Vista faster than our PCs did.
Source: "Mac vs. PC: The Ultimate Lab Test for New Desktops & Laptops" by Glenn Derene, published in Popular Mechanics.