I have built several sophisticated Vex robots so far, in addition to many LEGO Mindstorms robots. At this point, I will agree 100% with Popular Science in saying that Vex is better than Mindstorms. I own several Mindstorms kits, plus one Vex kit. I have been involved with a half dozen Lego Mindstorms competitions and three Vex competitions. Ever since I bought my Vex kit, I have never touched my Mindstorms kits.
With Vex, you can run up to eight motors or servos, as compared to just three with the RCX. You have 16 analog/digital input/output ports to use. Vex currently has six sensors (Ultrasonic, Shaft Encoders, Line Following, Light Sensor, Limit Switch, Bumper Switch), although any digital or analog sensor can be used. I have used custom IR short and long range sensors and potentiameters on my Vex robots.
The eight motor ports generate PWM signals, so any PWM device can be plugged into these. This includes regualar servos or speed controllers.
After being involved with the Educational FIRST Robotics competition, which involved LEGO Mindstorms, Vex Robotics, and full-size robots, I can say that LEGO Mindstorms are best suited students aged 9-14. The Vex Robotics kit, with a much greater sophistication, blows away the Mindstorms kits for students aged 14+. The Vex kits are way better at teaching programming, engineering, mechanical design, and robot competitions than the LEGO Mindstorms kits.
Here are some pictures of my current VEX robot, which scores 'tetras' and is a complete 1:3 scale replica of the Team 228 FIRST Robotics Competition robot.
Here is a close up of the single stage elevator gearbox and the arm gearbox. The arm will lift close to 3 lbs. Everything here is made out of only Vex parts.
Here is a closeup of the drive train on my Vex robot. As before, everything here is Vex only parts. Including the omni-wheels.
Last, but not least, is my favorite robot of all time. This is called the Beer Bot and was built by John V Neun and Chris Carnevale. The robot finds a bottle of beer, pops tha cap off, and pours it into a cup, and then deposits the cup down on the table. More cool Vex robots can be found at VexLabs.com
DannyStaple: Edited to thumbnails. Click images for larger versions.